Columbia Disaster...

A timeline of the final minutes of the shuttle flights and the hours following it (all times EST):

8:15 a.m.

Space shuttle Columbia fires its braking rockets and streaks toward touchdown.

8:53 a.m.

Ground controllers lose data from four temperature indicators on the inboard and outboard hydraulic systems on the left side of the spacecraft. The shuttle is functioning normally otherwise, so the crew is not alerted.

8:56 a.m.

Sensors detect rise in temperature and pressure in tires on the shuttle's left-side landing gear.

8:58 a.m.

Data is lost from three temperature sensors embedded in the shuttle's left wing.

8:59 a.m.

Data is lost from tire temperature and pressure sensors on the shuttle's left side. One of the sensors alerts the crew, which is acknowledging the alert when communication is lost.

Approximately 9 a.m.

All vehicle data is lost. The shuttle is 207,135 feet over north-central Texas and is traveling about Mach 18.3. NASA officials try to re-establish communication for several minutes.

Texas and Louisiana residents report a loud noise and bright balls – shuttle debris -- in the sky.

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Columbia Disaster...

9:16 a.m.

NASA Administrator Sean O'Keefe contacts President Bush and Homeland Security Director Tom Ridge when the shuttle does not land on schedule. O'Keefe later says Bush "offered full and immediate support."

9:29 a.m.

NASA declares an emergency.

9:44 a.m.

NASA warns residents of affected area to stay away from debris.

11 a.m.

The flag atop the countdown clock at Florida's Kennedy Space Center is lowered to half-staff. Flags at the White House and Capitol soon follow.

12:15 p.m.

Bush returns to Washington from Camp David in a speeding motorcade.

1 p.m.

NASA administrators officially announce the loss of the shuttle and all aboard.

1:25 p.m.

Bush calls Israeli Prime Minister Ariel Sharon and speaks with him about 5 minutes. The shuttle was carrying the first-ever Israeli astronaut, payload specialist Ilan Ramon.

2 p.m.

The president addresses the nation from the Cabinet Room at the White House. "Columbia is lost," he says. "There are no survivors."

3:20 p.m.

NASA suspends shuttle flights for the length of the investigation.