American spokesman Tim Smith says the pilot of Flight 611 was using an automatic docking system when the incident happened Thursday.
DFW spokesman David Magana says the airport officials are investigating. Damage estimates were not immediately released.
The right wing of MD-80 from Charlotte, N.C., struck part of the ladder on the truck, as the plane arrived with a passenger having some medical problems. Magana says the emergency vehicle, parked in a fire lane, was with medical personnel awaiting the arrival.
Other passengers say that a man, with apparent diabetic problems, was talking and seemed alert at the end of the flight.