First defection of MiG-21 Syrian Air Force fighter aircraft pilot 2206121.

The pilot was identified as Col. Hassan al-Mirei Hamadeh, and his defection raised questions about whether fealty to President Bashar al-Assad was fraying in the air force, the military branch regarded as closest to the Assad family, which has controlled Syria for four decades. Mr. Assad’s father, Hafez, was an air force officer.

The defection of this pilot was a triumph for the rebels who are fighting to overthrow Assad. The air force is considered fiercely loyal to the government, and the defection suggests some of Syria’s most ironclad allegiances are fraying. A spokesman for the rebel Free Syrian Army, Ahmad Kassem, said the group had encouraged the pilot to defect and monitored his activity until the jet landed safely in Jordan. He said the pilot was based in southern Syria.

Syria’s state-run TV reported earlier in the day that authorities had lost contact with a MiG-21 that was on a training mission in the country. The report gave no further details.

Jordanian Information Minister Sameeh Maaytah confirmed that the pilot had defected.

The defection is a sensitive issue for Jordan, which wants to avoid getting dragged into the Syrian conflict. Jordan already has taken in 125,000 Syrian refugees, including hundreds of army and police defectors, and Syria is seeking their extradition.