December 1998
Construction begins on the Deepwater Horizon oil rig in Ulsan, South Korea, by Hyundai Heavy Industries Shipyard.
February 2001
The rig is delivered and valued at more than $560m.
20 April 2010
Explosion and fire on the BP-licensed Transocean drilling rig Deepwater Horizon, located in the Gulf of Mexico. Eleven people are reported missing and approximately 17 injured. A blowout preventer, intended to prevent release of crude oil, failed to activate.
Deepwater Horizon oil rig fire leaves 11 missing
22 April
Deepwater Horizon rig sinks in 5,000ft of water. Reports of a five-mile-long oil slick. Search-and-rescue operations by the US National Response Team begin.
23 April
The US coast guard suspends the search for missing workers, who are all presumed dead. The rig is found upside down about a quarter-mile from the blowout preventer. A homeland security department risk analysis says the incident "poses a negligible risk to regional oil supply markets and will not cause significant national economic impacts". White House press secretary Robert Gibbs says: "I doubt this is the first accident that has happened and I doubt it will be the last."
Deepwater Horizon clean-up workers fight to prevent disaster
24 April
Oil is found leaking from the well for the first time. A homeland security report on critical infrastructure says the problem has "no near-term impact to regional or national crude oil or natural gas supplies."
25 April
US coast guard remote underwater cameras report the well is leaking 1,000 barrels of crude oil per day (bpd). It approves a plan for remote underwater vehicles to activate a blowout preventer and stop the leak.
Underwater robots try to seal well
26 April
BP's shares fall 2% amid fears that the cost of cleanup and legal claims will hit the London-based company hard. Roughly 15,000 gallons of dispersants and 21,000ft of containment boom are placed at the spill site.
27 April
The US departments of interior and homeland security announce plans for a joint investigation of the explosion and fire.
The coast guard announces it will set fire to the leaking crude to slow the spread of oil in the Gulf.
Oil spill to be set on fire to save US coast
Minerals Management Service (MMS) approves a plan for two relief wells.
The homeland department's infrastructure and risk analysis centre reports: "Release of crude oil, natural gas and diesel fuel poses a high risk of environmental contamination in the Gulf of Mexico."
BP reports a rise in profits, due in large part to oil price increases, as shares rise again.
BP profits jump after oil price rise
In pictures: fire on the Deepwater Horizon oil rig
28 April
The coast guard says the flow of oil is 5,000bpd, five times greater than first estimated, after a third leak is discovered.
Gulf oil spill 'five times' larger than estimated
Controlled burns begin on the giant oil slick.
BP's attempts to repair a hydraulic leak on the blowout preventer valve are unsuccessful.
29 April
President Obama talks about the spill at the White House, his first public comments on the issue. He pledges "every single available resource", including the US military, to contain the spreading spill, and also says BP is responsible for the cleanup.
Louisiana declares a state of emergency due to the threat to the state's natural resources, as the oil slick approaches land.
Deepwater Horizon oil slick to hit US coast within hours
Oil spill approaches Gulf coast, threatening economy and environment
BP's shares plummet as the crisis continues.
30 April
An Obama aide says no drilling will be allowed in new areas until the cause of the Deepwater Horizon accident is established.
US bans new drilling in Gulf of Mexico
The US justice department announces that a team of lawyers is monitoring the spill. Safety inspections of all 30 deepwater drilling rigs and 47 deepwater production platforms are ordered.
BP chairman Tony Hayward says the company will take full responsibility for the spill, paying for all legitimate claims and the cost for the cleanup.
Conservationists warn of impending disaster for wildlife in the area of the spill.
Conservationists warn of 'true catastrophe' for wildlife
Interactive graphic: species under threat
1 May
The coast guard announces the leak will affect the Gulf shore.
2 May
US officials close areas affected by the spill to fishing for an initial period of 10 days.
Obama visits the Gulf coast to see cleanup efforts first hand.
Barack Obama flies to Louisiana as BP's Deepwater Horizon oil spill spreads
BP starts to drill a relief well alongside the failed well.
An additional 30 vessels and 1,000 responders are deployed to the Gulf coast.
BP's efforts to contain the leak
4 May
BP executives face Congress in a closed session, as the White House backs a Senate proposal to increase the limit on liability payouts from $75m to $10bn (£6.5bn) for the cost of a spill.
Deepwater Horizon oil spill sparks calls for $10bn levy on BP and drilling ban
5 May
BP successfully attaches a valve to the end of the broken drilling pipe at the Macondo well in a bid to end the flow of oil into the US Gulf. BP says one of the three leaks has been shut off by capping a valve, but that would not reduce the amount of oil gushing out. Officials conduct controlled burns to remove oil from the open water.
BP stems one of three Deepwater Horizon oil leaks, US coast guard says
The White House attempts to limit the political fallout by documenting actions taken since the leak began.
Obama attempts to limit political fallout
In pictures: Deepwater Horizon oil spill closes in on US coastline
6 May
BP confirms the arrival of three huge containment domes designed to collect much of the 5,000bpd leaking into the US Gulf from the Macondo blowout.
Containment dome reaches Gulf oil spill scene
The department of justice asks Transocean to preserve evidence in connection with the explosion and sinking of the rig.
Toxic pink oily seawater washes ashore on the Chandeleur Islands off the Louisiana coast, an important nesting and breeding area for many bird species.
Hayward tells the BBC that the blowout preventer owned by Transocean was at fault for the leak. BP, he said, "will be judged not on the basis of an accident that, you know, frankly was not our accident".
Analysts put the cost of the spill for BP at £15bn.
BP 'facing £15bn loss' over Gulf of Mexico oil spill
7 May
BP engineers use undersea robots to move the containment chamber over the larger of the two remaining leaks on the seabed. This containment method has never before been attempted at such a depth.
Efforts to close valves on a failed blowout preventer with underwater robots are abandoned.
Deepwater team attempts to put 100-tonne box over blown-out oil well
Video recreation of cofferdam method
A fishing ban for federal waters off the Gulf is extended to 17 May.
8 May
BP's containment dome hits a snag when a buildup of crystallised gas forces engineers to postpone efforts to place the chamber over the oil leak and draw the oil to the surface.
Quick fix dashed as BP tower fails to contain oil
A BP report blames the explosion on a methane bubble.
Blast triggered by methane bubble, report shows
Tar balls suspected to come from the leak wash up along a half-mile stretch of Dauphin Island, Alabama.
9 May
BP says it might try to plug the undersea leak by pumping materials such as shredded tyres and golf balls into the well at high pressure, a method called a "junk shot".
10 May
BP announces plans to place a small containment dome, known as a "top hat", over the blown-out well to funnel oil to the surface, as Hayward holds a press conference.
11 May
At a hearing before the Senate committee on energy and natural resources, representatives of the three oil companies involved in the Deepwater drilling blame each other for the accident. Halliburton, which cemented BP's well, claims to have met BP's stated requirements for the task and cites the failure of Transocean's blowout preventer. Transocean's CEO says the blowout preventer was successfully tested a week before the accident; he also blames BP and Halliburton for the inadequate cementing believed to have led to the explosion. BP's president says that Transocean, as owner/operator of the drilling rig, is responsible for safety.
Gulf oil spill hearing - as it happened
12 May
After the failure of the four-storey-high dome to draw oil from the major leak, BP lowers a five-foot-high dome to attempt to cover the smaller leak.
The congressional hearing is told BP, Halliburton and Transocean ignored safety warnings in the hours before the Deepwater explosion.
Firms ignored warning signs before blast, inquiry hears
13 May
Steve Wereley, a researcher at Purdue University, tells the press he believes the well is leaking 70,000 bpd.
BP releases underwater footage of the effort to stem the leak.
First underwater video footage of oil leak
The New York Times reports that "a half-dozen current and former agency scientists" for the Minerals Management Service (MMS) claim they were "regularly pressured by agency officials to change the findings of their internal studies if they predicted that an accident was likely to occur or if wildlife might be harmed". The article states that the MMS has allowed hundreds of drilling projects without obtaining legally required permits.
US said to allow drilling without needed permits
14 May
BP plans to insert a 4in-tube into the ruptured 21in riser pipe that would take the oil to the surface. If that fails, they will use the small containment dome that has already been lowered. Both methods are intended to reduce, not to stop, the leak.
BP using undersea robots to try to plug Gulf oil leak
BP boss admits job on the line over Gulf oil spill
Obama complains: "I did not appreciate what I considered to be a ridiculous spectacle during the congressional hearings into this matter. You had executives of BP and Transocean and Halliburton falling over each other to point the finger of blame at somebody else … it is pretty clear that the system failed, and it failed badly."
16 May
The tube begins to draw oil to the surface. The volume of oil travelling through the tube is gradually increased to avoid the hydrate formation that doomed the large containment dome.
Submerged oil plumes suggest gulf spill is worse than BP claims
18 May
Obama plans to establish an independent commission to investigate the oil leak, according to an anonymous administration official.
As the spill continues to spread, the no fishing zone is doubled to 19% of the Gulf waters.
Atlantic coast now under threat as current spreads Gulf oil slick
20 May
BP reports that the amount of oil drawn off by the tube has increased to 5,000 bpd. Given that BP had previously estimated the entire leak at 5,000 bpd and the tube only draws off a fraction of the spill, the leak must be much larger than previously estimated.
Experts testifying at the congressional hearing put the figure at 20,000-100,000 barrels per day.
How big is the slick from BP's Deepwater Horizon?
24 May
The tube inserted into the leaking pipe captures much less oil than expected.
BP admits Deepwater rescue is capturing less oil
26 May
BP pumps thousands of barrels of mud into the well in an attempt to plug the leak. The process, known as top kill, fails to overcome the flow of oil.
A White House leak shows Obama ended a briefing with the terse command: "Plug the damn hole."
White House leak reveals Barack Obama's reaction to news of oil spill
30 May
Hayward causes outrage after telling reporters, "There's no one who wants this over more than I do. I would like my life back."
BP's clumsy response to oil spill threatens to make a bad situation worse
1 June
US launches a criminal investigation into the oil spill.
BP could face ban as US launches criminal investigation
2 June
Titanic director James Cameron assists the clean-up process.
James Cameron enters fight against oil spill
3 June
BP begins an advertising campaign in the US aimed at boosting opinion. Hayward features in the first.
America's toughest job: fronting BP's television commercials
BP faces political flack over its decision to pay out more than $10bn (£6.8bn) in dividends to shareholders, despite the deepening crisis.
BP to go ahead with $10bn shareholder payout
4 June
Attempts to place a cap over the valves that were meant to prevent the rig from leaking show signs of success.
BP shares top risers as engineers assess latest oil spill operation
6 June
BP announces the containment cap is capturing 10,000 barrels of oil a day; approximately half the total amount being leaked.
BP capturing '10,000 barrels of oil' a day from Gulf of Mexico
7 June
The widows of two of the oil rig workers give testimony before a congressional committee.
Deepwater Horizon widow asks: how do I tell my children their father is dead?
8 June
In an interview on NBC Obama says he would have sacked BP's chief executive if he had been working for him.
'If he was working for me I'd sack him' – Obama turns up heat on BP boss
11 June
David Cameron calls BP's chairman, Carl-Henric Svanberg, to a meeting at Downing Street to discuss the oil disaster.
David Cameron caught between Tory right and Obama
12 June
Scientists double their estimate of the scale of the spill to 40,000 barrels a day.
Scale of BP oil leak revised up to 40,000 barrels a day
14 June
Obama compares the BP oil spill to 9/11.
Barack Obama compares oil spill to 9/11
15 June
Fitch ratings agency cuts BP's credit rating as the cost of the spill continues to escalate.
BP credit rating slashed as oil spill costs mount
16 June
BP agrees to a $20bn (£13.5bn) downpayment towards compensation for victims of the oil spill.
Barack Obama's pound of flesh: $20bn compensation and no BP dividends
Actor Kevin Costner provides the clean-up operation with oil-water separation machines he developed with his brother.
Kevin Costner's oil-water separation machines help with clean-up
17 June
Hayward is accused by members of the US Congress of "stonewalling" after failing to answer a series of questions about the spill's causes.
Tony Hayward stonewalls Congress
18 June
BP's credit rating is downgraded by Moody's after expressing concern at the escalating cost of the cleanup and the potential cost of litigation claims.
BP credit rating downgraded after Tony Hayward's grilling by Congress
19 June
One of BP's partners, Anadarko Petroleum, refuses to accept any responsibility for the Deepwater Horizon explosion despite owning a quarter of the well. Its chief executive, Jim Hackett, says BP's actions probably amounted to "gross negligence or wilful misconduct".
BP oil spill caused by 'negligence or misconduct', says drilling partner
20 June
Photographs of Hayward attending a yacht race on the Isle of Wight with his son cause anger in the US.
BP chief's weekend sailing trip stokes anger at oil company
21 June
A Deepwater Horizon worker claims that the oil rig was leaking several weeks before it exploded.
Deepwater Horizon worker claims oil rig leaking weeks before explosion
22 June
Hayward fails to make an appearance at a gathering of the oil industry on the same day that control of the oil disaster passes to American Bob Dudley. Greenpeace protesters storm the stage during his replacement's speech.
BP's beleaguered Tony Hayward disappears from view
Protesters disrupt BP speech as Tony Hayward pulls out
23 June
An accident puts BP's oil cap out of action, allowing oil to flow unhindered for several hours.
Gulf oil spill flow increases after accident forces BP to remove cap
25 June
BP shares hit a 14-year low of 304p after the clean-up bill reaches $2.35bn.
BP share slide as oil spill bill climbs to $2.35bn
28 June
Russia's top energy official says he expects Hayward to step down soon. BP denies he is close to resigning.
Tony Hayward set to step down, Russian official claims
The Guardian publishes a letter from 171 artists, critics and writers complaining about BP's sponsorship of Tate Britain.
Curators, crude oil and an outdated cultural mix
Protesters disrupt Tate Britain's party celebrating 10 years of BP sponsorship, throwing molasses over the steps of the gallery.
Art activists take on the Tate crowd over BP
30 June
Hurricane Alex causes heavy seas, disrupting BP's clean-up efforts.
First hurricane of season hits BP oil spill clean-up
5 July
BP announces the cost of the oil spill has now risen to over $3bn. The company asks its partners, Anadarko and Mitsui Oil Exploration, to contribute almost $400m.
BP asks oil spill partners to pay $400m
6 July
BP's share price rises as speculation mounts that the company is looking for international investors.
BP shares rise on hopes of international rescue
7 July
There are more than 27,000 abandoned oil wells in the Gulf of Mexico from a host of companies including BP, according to an investigation by Associated Press, which describes the area as 'an environmental minefield that has been ignored for decades'. Some of them date back to the 1940s. State officials estimate that tens of thousands of them are badly sealed.
Abandoned oil wells make Gulf of Mexico 'environmental minefield'
9 July
A US appeals court rejects the federal government's effort to restore an offshore deepwater drilling moratorium, opening the door to resumed drilling in the Gulf of Mexico while the legal fight continues. The same appeals court is expected to hear arguments on the merits of the moratorium case in late August or early September.
US appeals court opens door to new drilling in Gulf of Mexico
11 July
BP begin their latest attempt to seal the leak. Robots remove a leaking cap from the well, to allow a replacement containment system to be installed.
BP begins new operation to seal off leaking Deepwater Horizon well
12 July
With the latest attempt to stem the leak reportedly going well, BP shares rise.
BP shares rise as Deepwater Horizon well repairs progress 'as planned'
A commission appointed by Obama to uncover the cause of the oil spill is told of "friction" between BP and Transocean, the operator of the Deepwater Horizon.
Barack Obama's investigation hears of 'friction'
13 July
BP successfully installs a new, more tightly fitting containment cap on the ruptured wellhead. The next step is to test the internal pressure in the well to establish whether the flow has been stopped.
New cap 'successfully installed' on leaking well
15 July
Hillary Clinton pledges to looks into claims BP lobbied for the release of the Lockerbie bomber.
BP faces Lockerbie allegations
BP stops the flow of oil for the first time in 87 days, raising hopes that it could be sealed off for good. The company says it will have to monitor the cap for 48 hours before it can be sure it will hold.
BP stops oil leak in Gulf of Mexico for first time since April
19 July
Fears about the new cap are raised after engineers detect seepage and a possible methane gas leak on the seabed. Admiral Thad Allen, who is in charge of the US government's response, has written to BP demanding answers to "undetermined anomalies at the wellhead". BP has yet to respond.
Shares in BP fall more than 5% on the news.
BP oil cap may not have stopped leak
BP shares lead FTSE 100 lower on new spill worries
David Cameron agrees to meet four US senators to discuss concerns that BP lobbied the British government ahead of the decision to release the Lockerbie bomber, Abdelbaset al-Megrahi, last year. The prime minister, who is embarking on a US visit, had previously stated that his schedule was too full to include a meeting.
Cameron to discuss Megrahi's release with US senators
20 July
Allen grants BP a further 24 hours to test the new containment cap, but warns that the government may insist on reopening the well if concerns over seepage intensify.
US gives BP 24 hours to monitor capped oil well
21 July
BP admits to using Photoshop to exaggerate the level of activity at the Gulf oil spill command centre. The picture, posted on the company's website, shows staff monitoring 10 giant video screens. In reality, three of the screens were blank.
BP admits using Photoshop to exaggerate oil spill command centre activity
David Cameron warns US legislators not to single out BP over oil damages. In an interview on ABC television he argues: "Would it be right to have legislation that independently targets BP rather than other companies? I don't think that would be right ... Would it be right to say that BP has to pay compensation for damages that were nothing to do directly with the spill? I don't think that would be right"
Don't single out BP over oil damages, David Cameron warns US