(CNN) -- The challenges inherent in getting a 162,000-pound aircraft off the ground and landing it safely are pretty obvious to most observers. But at cruising altitude, above 10,000 feet, pilots face a different critical challenge: staying focused.

Two Northwest Airlines pilots lost their licenses Tuesday after they missed their destination by 150 miles because they weren't paying attention to their instruments or air traffic controllers.

No one was hurt in the incident last week, but the Federal Aviation Administration called Capt. Timothy B. Cheney and first officer Richard I. Cole "extremely reckless" and said they put the public in danger.

When cruising over great distances, "it's very easy to be distracted because there's not a whole lot going on," said Emilio Corsetti III, a 30-year commercial pilot with American Airlines who has written numerous magazine articles about aviation.

An airliner's entire flight can be programmed; once that program is activated, "the plane will fly to its destination without any input from the pilot at all," he said.

Cheney and Cole told investigators they lost track of time while using their personal laptop computers to look at new airline scheduling software related to Northwest's merger with Delta Air Lines. They were piloting the Airbus A320 from San Diego, California, to Minneapolis, Minnesota, a flight that should take 3 hours and 42 minutes.

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