John Morris of Fort Collins, Colo., was headed home from Dallas when flight attendants were told by the pilot that using seat-belt extensions to secure Morris was not considered proper by the Federal Aviation Administration, The Denver Post reported Tuesday.
Morris was removed from the plane but was able to board a later Frontier flight to Denver without objections from its pilot.
Frontier apologized for the Sunday incident in an e-mail statement Monday and said an investigation was underway.
The statement said the first pilot "was seeking to do the right thing to ensure the safety of all involved."
Frontier said it would be taking steps to see that the situation is not repeated.