One of the problems plaguing the program is that the exact demand for the aircraft is still unknown. With demand unknown, it's hard for the program to justify increasing costs and has led the Pentagon to cut back on some program flight tests and to reconsider some of the program features like the development of a second engine for the aircraft.

In November, reports surfaced that with the increasing cost overruns many of the countries that had intended to purchase the F-35 are now reconsidering the number of aircraft they will purchase. The Dutch parliament for example could reduce the number of aircraft is purchases from the planned 85 to 57 to reduce costs. With several countries, reconsidering their purchases the overall orders of the F-35 could be cut in half.

Military.com reports that the F-35 program is behind schedule and over budget. According to reports that were prepared by the Defense Contract Management Agency for the Defense Department, Lockheed and its contractors are months behind in deliveries of key components and test aircraft for testing.

Even worse than delays is the fact that the reports say the entire development budget for the aircraft could be exhausted within a year. The Pentagon has already said that the development of the aircraft could take two more years and billions more in funds.

Dan Crowley, a senior Lockheed executive running the F-35 program said that the reports about delays and cost overruns were mostly true. However, he maintains that the program is past most of the major delays.

He said, "We're not drawing farther from the schedule. We're going to meet the schedule beginning in 2011."

A new F-35 aircraft had its first test flight on Saturday and the plane was only the fourth aircraft to make a test flight since the contract was awarded to Lockheed in 2001. So far, only seven of the 13 test aircraft have been completed while all 13 aircraft were supposed to have been tested and completed for testing in early October.

The test aircraft that flew this weekend was a milestone for the program. The airplane was the first conventional takeoff F-35A model, the previous aircraft that were tested were the F-35B models designed for short-takeoff-vertical landing. The Two F-35B models have made a total of 37 combined test flights in the last 18 months.

Military.com quotes aerospace engineer Hans Weber saying, "The airplane is so ambitious, it was bound to have problems."

Some fear that the Pentagon might cut flight tests and test aircraft further to save money for the program. Webber said, "You need to do the testing the engineers originally said needed to be done."

As flight tests progress any changes made to rectify problems found in testing will have to be fitted to the other aircraft. This will further drive costs for the program up.