Mr. Trump’s fleet of private aircraft, which includes a Boeing 757, a Cessna Citation X and three Sikorsky helicopters, whisks the billionaire executive to Republican primary events in far-flung locales, some of them difficult to reach by commercial planes.

The fleet also allows Mr. Trump to promote his brand. He garnered valuable publicity at the recent Iowa State Fair, for example, by giving children free rides in one of his helicopters with a huge Trump logo on the side.

“It’s a massive, unbelievable competitive advantage,” said Dave Carney, a GOP campaign consultant who was chief strategist for Rick Perry’s 2012 presidential primary campaign. “Having access to a private jet is the single most important asset to any national political campaign. It’s hugely expensive, but it gives you the ability to set your own schedule.”