The U.S. Navy recently offered contractors details on what it would like to see in its first production aircraft carrier-based drone. Two San Diego businesses are pursuing the program, which is expected to be worth billions of dollars.

The program would follow two experimental, carrier-based drones designed in San Diego by Northrop Grumman Corp.

A draft request for proposals went to four aircraft makers, including two in San Diego, on April 17, and was not made public.

The recipients include Northrop Grumman (NYSE: NOC), which bases its unmanned aircraft programs in Rancho Bernardo, as well as General Atomics Aeronautical Systems Inc. of Poway. Also receiving the draft request were Boeing Co. (NYSE: BA) and Lockheed Martin Corp. (NYSE: LMT). In August, the four businesses received preliminary design review contracts worth $15 million.

According to published reports, the Navy has been weighing the requirements for the carrier-based drone. For example, it has been deciding how stealthy it wants the aircraft to be.

The purpose of the document issued April 17 “is to solicit industry to design, develop, assemble, deliver, test and integrate the air segment into the Uclass system,” said a statement from the Naval Air Systems Command in Patuxent River, Md. Uclass stands for Unmanned Carrier Launched Airborne Surveillance and Strike aircraft.

A command spokeswoman said the Navy will issue its final request for proposals in the summer, and expects to award a contract in 2015.

In addition to the air segment, the Navy will award contracts for the carrier segment of the program, as well as a control system and connectivity segment.