According to released transcripts, a caller from the Port Authority police desk tells a La Guardia Airport control tower employee that, “they are considering [the crashes into the WTC] a criminal act.” The control tower employee replies, “We believe that, and we are holding all aircraft on the ground.”
[Associated Press, 12/29/2003] La Guardia is one of two major New York City airports, and the Port Authority patrol both the WTC and the city’s airports.