Both the FBI and homeland security issued this warning for U.S. airspace. The threat, they say, is for small planes that terrorists may use in combination to strike the U.S.
Experts say al Qaida is not just interested in large-scale attacks, but may be plotting smaller attacks that are easier to pull off. There are a lot of these small planes, 228,000 general aviation planes at 4,000 airports nationwide.
Monitoring all of them would be impossible, but already those who fly and monitor these planes are being told to be on high alert.
"Two FBI agents actually came in and introduced themselves and told me about the possibility of, not a specific threat, but that al Qaida was planning to use general aviation to harm us here in America," said flight instructor Bob Wood with Diamond Aviation.
This isn't the first time small planes have been a concern with respect to terrorism. After September 11, 2011, the government temporarily grounded crop dusters because there was concern about them being used to spread a deadly agent.
