Investigators are searching the wreckage of a plane for clues to help them understand what caused it to crash at Madrid's main airport on Wednesday.
The Spanair plane was on its way to the Canary Islands, when it swerved off the runway as it tried to take off.
One hundred and fifty-three passengers died in the crash. Nineteen people survived, but some were badly hurt.
Three days of official mourning have been declared in the city, which is the capital of Spain.
The crash is the worst in the country for 25 years, and it's important to remember that incidents like this are very rare.
Spanish Prime Minister Jose Luis Rodriguez Zapatero is expected to visit the survivors in hospital.
King Juan Carlos will visit Barajas airport, where the crash happened, and families of the people who were on the plane.
Leaders from around the world have been saying how sorry they are about the crash, and sending Spain messages of sympathy.