Another day, another delay for the space shuttle Endeavour, this time until the middle of May.

The mission was supposed to originally launch on April 19, and it now may not do so until the middle of May, if not later. NASA said technicians and managers met Friday afternoon and determined the space shuttle Endeavour will launch no earlier than Monday, May 16 at 8:56 a.m. EDT. The mission will be the last for the shuttle, which will go into retirement immediately afterwards.

The shuttle was originally delayed because of a scheduling problem with a Russian spacecraft. Then it was delayed again because of a problem with its heating auxiliary power unit-1 (APU-1). The latest update from NASA said the Load Control Assembly-2 (LCA-2) box in the orbiter's aft compartment, where the heating unit was located, was removed and being worked on by technicians.

NASA will air a news conference Monday at 3 p.m., to discuss the status of the work. The shuttle crew includes Commander Mark Kelly, Pilot Gregory H. Johnson and Mission Specialists Michael Fincke, Greg Chamitoff, Andrew Feustel and European Space Agency astronaut Roberto Vittori.

During the 14-day mission, Endeavour and its crew will deliver the Alpha Magnetic Spectrometer (AMS) and spare parts including two S-band communications antennas, a high-pressure gas tank and additional spare parts for Dextre. After it finishes up, NASA will conclude the space shuttle program with the Atlantis. Following that, the three remaining space shuttles and a fourth prototype will head to museums.

A NASA official told SPACE.com, the cost of the delay would be at least $500,000, if not more. This is mainly due to the cost of de-tanking, where the fuel propellant is drained for an external tank.

Along with being the final trip for the Endeavour, this mission is the penultimate mission for the space shuttle program. It also features commander Kelly, husband of congresswoman Gabrielle Giffords, who was nearly shot to death earlier this year.  President Barack Obama was in Florida last Friday for the proposed launch and met with Commander Kelly and his team. He also met with Giffords.

Follow Gabriel Perna on Twitter at @GabrielSPerna