The U.S. space agency is seeking new technologies that could benefit from testing during flights on an airplane that simulates the weightlessness of space.

The National Aeronautics and Space Administration said such technologies might improve air and space vehicle capabilities and support future systems used in space exploration.

"To prepare technologies for space applications, it is important to demonstrate they work in a zero-gravity environment," NASA said.

"This unique testing environment can be provided in an aircraft flying repeated parabolic trajectories which create brief periods of zero gravity. The aircraft also can simulate reduced-gravity levels similar to those found on the surface of the moon or Mars."

The testing opportunities are being offered to U.S. companies, individuals, academic or research institutions and government agencies. NASA said it will provide free flight time for the tests, while project teams will be responsible for all other expenses.

Proposals are due by March 20. Flights to demonstrate the technologies will be conducted during August from Ellington Field in Houston. NASA expects to select at least 20 projects for this round of test flights, pending availability of funding.