A medical helicopter pilot flying over Missouri was sending and receiving text messages before crashing in 2011, the first time such distractions have been implicated in a fatal commercial aviation accident.

The U.S. National Transportation Safety Board (NTSB), which meets on Tuesday to assign a cause for the accident that killed four people including a patient, documented seven texts sent and received by the pilot.

The Air Methods Corp. helicopter crashed in a field after running out of fuel, according to preliminary NTSB reports. Use of electronic devices by pilots during flight was prohibited by company rules, the reports said.

“This is a classic example of dividing attention in a way that compromises safety,” said David Strayer, a psychology professor at the University of Utah in Salt Lake City who has studied how personal electronic devices cause distraction.

This is the first time the NTSB has uncovered evidence of texting or mobile-phone use during a flight involved in a fatal accident, NTSB spokeswoman Kelly Nantel said in an e-mail.

The crash on Aug. 26, 2011, in Mosby, Mo., killed Terry Tacoronte, a patient who was being flown from one hospital to another. Pilot James Freudenbert, flight nurse Randy Bever and paramedic Chris Frakes also died. The helicopter was being operated under the name LifeNet.

Air Methods did not respond immediately to requests for comment. The Englewood, Colo.-based firm says on its website that it operates more than 300 air-medical bases in 48 states.

Freudenbert, 34, received four texts, three of them from a friend at work, and sent three others during the flight, according to NTSB records. Another 13 texts were logged on his phone in the 71 minutes before the flight, including two during a previous flight, according to NTSB records.

Freudenbert, who told the co-worker he hadn’t slept well the night before, failed to refuel the helicopter before flying to Bethany, Mo., to pick up Tacoronte, according to NTSB records. He realized his mistake after landing and discussed where to get more fuel with a company dispatcher. He was headed to Midwest National Air Center Airport in Mosby when the helicopter went down.

Freudenbert radioed a dispatcher after takeoff that he had enough fuel to fly 45 minutes; helicopters carrying passengers for hire must carry a 20-minute fuel reserve beyond what they need to get to their destination, according to NTSB records. The copter was aloft for 30 minutes before it crashed, and Freudenbert never radioed that he was having an emergency. A powerless helicopter should be able to land safely.