Private aviation returned yesterday to Reagan National Airport, more than four years after restrictions were imposed because of the Sept. 11, 2001, terrorist attacks.

The first aircraft arrived from Teterboro Airport in New Jersey about 7 a.m. The flight was permitted after the Transportation Security Administration introduced new rules that require passengers and crew members to undergo background checks.

A certified, armed security officer must accompany each flight, and some trips require a federal sky marshal.

"This is a first step," said Rep. Thomas M. Davis III (R-Va.). "There are still a ton of regulations."

Commercial airline flights at the airport resumed about a month after Sept. 11, 2001. Extensive lobbying by local officials and business leaders -- as well as congressional intervention -- was needed to convince federal authorities that the airport was safe for general aviation.

Opponents of opening the airport to private planes argued that it would be difficult to distinguish planes that had permission to fly in the restricted airspace over Washington from those that didn't have permission.

Pilots have strayed into the airspace hundreds of times since it was declared off-limits just before the Iraq war in 2003. Fighter jets authorized to shoot down intruders have escorted many errant planes to airports. Until yesterday, most private flights were diverted to Manassas Regional Airport, about 30 miles southwest of Reagan National.