BBC News Online's Kevin Anderson in Washington

A teenager's suicidal flight has the US questioning security at small airports and at a critical military base.

The 15-year-old's flight took him over MacDill Air Force base - home to Central Command, which is directing the war in Afghanistan.

The incident has renewed security concerns about not only large commercial aircraft but also smaller planes and their pilots.

But private pilots are warning against overreaction, saying that small aircraft make poor tools in the hands of terrorists and that simple steps could provide greatly increased security at the nation's smaller airports.

General aviation security

Teen Charles Bishop was told by his instructor to conduct a pre-flight check, but he took off without him.

Investigators said that no regulations were violated in allowing the teen to carry out the safety check without his trainer.

But flight schools are now examining the practice of allowing students to conduct unsupervised pre-flight checks.

There are some 4600 general aviation airports and some 200,000 private aircraft in the US. They range from large airports that have both commercial airline and general aviation services to small airports that are not much more than a grass landing strip.

General aviation flights were grounded for a short time after 11 September, and they still remain grounded in the Washington DC metropolitan area.

But security measures are far less for private planes than they are for commercial flights.

"Generally, in general aviation, because it is not public, in the sense that not just anybody can board, security requirements are less than they are for airline aircraft," said William Schumann, spokesman for the Federal Aviation Administration.

There are no regulations that private aircraft have additional security measures apart from door locks and ignition keys, he said, although general aviation groups are encouraging plane owners to increase security.

To apply for pilot's licence, potential pilots must receive a medical certificate from an FAA-certified physician, and when people apply for a licence, they authorise the FAA to check the national drivers registry to check whether they have ever been convicted of driving under the influence of drugs or alcohol, Mr Schumann said.

Military review

Before he crashed the plane into the 28th storey of the Bank of America, the teen flew briefly over MacDill Air Force Base, home to US Central Command, which is overseeing US forces in Afghanistan.

A spokesman at MacDill said the base was notified when the plane was about three miles away.

MacDill is home base for General Tommy Franks, who is overseeing operations in Afghanistan

Pentagon officials and spokesmen at the MacDill Air Force Base defended security measures at the sensitive military installation.

"There was not a perceived threat," said Admiral John Stufflebeem, adding, "He didn't take off with a flight full of explosives."

A Coast Guard helicopter intercepted the boy's plane and tried to get him to land without success.

Two military jets were scrambled from Homestead Air Force base 200 miles away but were unable to arrive before the boy crashed.

Admiral Stufflebeem did say that the Federal Aviation Administration, the North American Aerospace Defence Command (NORAD) and the commander of MacDill would all be reviewing the response.

"How long did it take to be recognized that this is something that has gone seriously wrong and warrants a military response? And that's going to have to be looked at to get answered," Admiral Stufflebeem said.

Call for increased security

Some critics complain that all that stands between a potential terrorist and another airborne attack is a chain-link fence.

But private pilots say that they police themselves and that the threat posed by private aircraft is small as evidenced by the limited damage caused by the crash in Florida.

Damage was limited to the immediate area where the plane crashed

No one was killed or injured apart from the teen, and the building suffered no major structural damage.

But private pilots are warning against overreaction and urging officials to take action to improve general aviation security.

The Aircraft Owners and Pilots Association said it was "taking the offensive to ensure that this weekend's tragic incident in Tampa, Florida, does not result in ill-considered regulations against general aviation."

"This was not a breach of security, this was an abuse of trust," said AOPA President Phil Boyer. "An apparently troubled young man who had legitimate access to an aircraft abused the trust of his flight instructor and stole the airplane with tragic results."

The AOPA, along with other general aviation organisations, has called for the government to adopt new tougher security standards for general aviation.

They call new difficult-to-counterfeit photo ID's for pilots. They say that the US government should review all existing and new pilot certificates to ensure that that the pilots are not on terrorist "watch lists."

Pilots renting or purchasing aircraft should be made to provide government-issued identification.

The group also called on pilots to secure their aircraft against theft, to increase their vigilance for suspicious activities around airports and to check the identity of their passengers.

"These recommendations would further ensure public confidence and raise additional barriers to terrorist use of general aviation," said AOPA President Phil Boyer.