Relief flights donated by airlines began to fly into Louis Armstrong International Airport (search) in New Orleans at a rate of about four an hour, beginning midday Friday.

Transportation Department spokesman Greg Martin said the planes will be bringing in supplies and leaving with people. Most of the flights will take refugees to Lackland Air Force Base (search) in Texas.

The first flight on Friday, he said, was a Spirit Airlines (search) MD-83.

The airport building and runway weren't damaged much by Hurricane Katrina (search), but navigational aids such as radar and runway lights weren't working.

Martin said the Federal Aviation Administration (search) was able to establish limited operations within a day of the hurricane. Work over the past few days allowed the airport and air traffic control to sustain a more systematic relief effort Friday.

Air traffic controllers in New Orleans are handling about 300 flights at any given time, Martin said. "All of them are providing humanitarian relief," he said.

The airport is now able to handle nighttime flights thanks to runway lights provided by the military, he said.

More than a dozen passenger airlines and their crews volunteered to provide emergency airlift to more than 25,000 New Orleans residents stranded after Hurricane Katrina.

They are Alaska Airlines, America West, American Airlines, ATA, Continental, Delta Air Lines, Jet Blue, Northwest, Southwest, United, US Airways and Air Canada.

Cargo carriers, including UPS, FedEX and ASTAR Air Cargo are also helping out.

Hundreds of private pilots have contacted their trade group, the Aircraft Owners and Pilots Association, asking what they can do to help, said Chris Dancy, AOPA spokesman.

Some pilots have set up a shuttle service out of Baton Rouge, La., to evacuate high-risk people to Texas. Others are flying damage-assessment missions over the damaged region and bringing in critical supplies.

A pilot in Louisville, Ky., is recruiting pilots to work with a group called Vacation Rentals for Families.com that is finding people who will open their vacation homes to Katrina evacuees.