The US Federal Aviation Administration has released the air traffic control recordings and transcripts of the whole US Airways Hudson River ditching incident on 15 January.
It reveals that between the Airbus A320 crew's first contact with New York's ATC just after take-off from LaGuardia airport until the captain notified his final commitment to ditching in the Hudson the elapsed time was 3min 56s, and 23s after that New York notified him they had lost radar contact.
From the time of the crew's advice to ATC that they had suffered power failure in both engines following a birdstrike and they were minded to return to LaGuardia, New York Departure Control periodically passed them appropriate advice about available runways at LaGuardia, Teterboro, and and Newark airports. Ater the A320 crew - callsign "Cactus 1549" - finally stated at 2029:21 UTC that "We can't do it [land at Teterboro], we're gonna be in the Hudson," the pilots were passed advice but did not reply.
Shortly after that, at 2029:51 New York control said: "Cactus fifteen forty-nine radar contact is lost, you also got Newark Airport off your two o'clock about seven miles." Cactus 1549 did not acknowledge that call.
When the crew first called New York Departure Radar at 2025:51 just out of LaGuardia they reported "seven hundred feet climbing [to] five thousand," and were immediately cleared to continue climb to 15,000ft. At 2027:32 the A320 was told to turn left onto heading 270deg, and four seconds later the reply came back: "Ah this is Cactus fifteen thirty-nine [sic] hit birds we lost thrust in both engines we're turning back to LaGuardia." After 5s New York responded: "Okay yeah you need to return to LaGuardia turn left heading of uh two two zero." Cactus acknowledged "two two zero," and the New York controller telephoned LaGuardia to stop take-offs because they had an emergency returning. It was only 29s after being given the heading to return to LaGuardia that the crew first intimated that the Hudson may yet turn out to be their best option, saying at 2028:11: "We're unable [to return to LaGuardia] we may end up in the Hudson." It was 1min 20s later, having considered and rejected Teterboro also, that the captain finally committed to the ditching option.
Throughout the recording New York Departure Control was dealing with ten other aircraft and made contact with LaGuardia and Teterboro airports to set them up to receive the emergency aircraft. The A320 crew never formally declared an emergency, and the frequency was not cleared of other traffic.