Federal regulators are concerned airlines and aircraft manufacturers won't meet the April deadline to install new bulletproof cockpit doors in all commercial aircraft.

A spokesman for large airlines said the companies believe they can do the work in time.

"It will be met," Air Transport Association spokesman Michael Wascom said Wednesday of the April deadline after a meeting in which federal regulators met with airlines, manufacturers and trade groups to find out how much progress they've made.

Yet some smaller airlines fear they won't get the doors in time to meet the deadline. They say the Federal Aviation Administration has been slow to approve new door designs, and they are worried they'll have to ground planes if the doors don't arrive in time.

"Most people in the industry, particularly the carriers, would like to proceed with this as soon as possible," said Ed Faberman, executive director of the Air Carrier Association of America, which represents smaller airlines. "But before that happens, we have to have doors that are certified."

The process of installing the new doors is halfway over, as federal officials in November gave the industry 18 months to meet the April 9, 2003 deadline. The FAA doesn't know how many planes have the new doors, and have asked the industry to supply that information.

The agency scheduled weekly meetings with the companies to get updates on the progress toward getting the new doors in about 7,000 U.S. planes by the April 9 deadline.

Wednesday's meeting reassured the agency that progress was being made, said FAA spokesman Scott Brenner. The FAA learned that more than 80 percent of the door designs should get approved by late September, Brenner said.

Once the door designs are approved, the manufacturers then produce them and deliver kits to the airlines, who are responsible for installing them.

Cockpit doors had been designed to provide a quiet office environment for pilots who were trained to negotiate with hijackers. After the Sept. 11 attacks, regulators decided pilots needed to be protected from attackers. Air carriers were given 90 days to secure cockpit doors with deadbolt locks and 18 months to install intrusion-proof doors.

The mandate posed an engineering challenge. Bulkheads have to be strengthened and electrical systems integrated. The doors themselves have to be heavy enough to be bulletproof, but not too heavy to weigh down the plane. They also have to allow pilots to exit in an emergency and to allow air to blow through to the cabin in case of rapid decompression.

"Its been difficult," said Jim Proulx, spokesman for The Boeing Co. "We've been asked to do stuff we've never done before."

The company, which has manufactured about 5,500 of the passenger planes registered in the United States, expects to get needed approvals for nine models by October, if not earlier.

Each Boeing door costs at least $29,000 and takes about 14 hours to replace. The federal government granted the airlines $17,000 to help pay for the doors.

Airbus North America, which made about 700 planes now registered in the United States, will be in compliance by the end of the year, company spokeswoman Mary Anne Greczyn said. Airbus and Boeing make most of the planes registered in the United States.

Another 1,900 planes owned by foreign carriers that operate in the United States will also have to get the new doors.