Endeavour's final ride may take a little longer than expected as the space shuttle will be delayed until at least May 8, NASA announced.

Over the weekend, technicians and engineers at NASA's Kennedy Space Center in Florida identified the reason for Endeavour's delay. The space shuttle was supposed to launch Friday afternoon; but it was scrubbed at the last minute due to a problem with its auxiliary power unit-1 (APU-1).

NASA says the failure is because of a power problem within the aft load control assembly-2 (ALCA-2), a box of switches controlling power feeds. NASA technicians will remove and replace the box, but that work and related testing will take several days to complete. Once the new box is installed, there is a one to two day period where it must be tested.

As a result, May 8 is the earliest the shuttle will be launched. Managers will meet over the next few days to discuss the possibility of a new launch date. After returning to NASA's Johnson Space Center in Houston, the six STS-134 astronauts, including commander Mark Kelly, will get some additional training before they return for the next launch attempt.

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. NASA spokesperson Allard Beutel said while NASA gets most of the propellant back to recycle and use again, some of it gets boiled off.

The Endeavour launch will be the final one for that space shuttle. It is also the penultimate mission for the space shuttle program. Not only is it the end of a historic ride for the well-traveled fleet, but it also will feature commander Kelly, husband of congresswoman Gabrielle Giffords, who was nearly shot to death earlier this year.

President Barack Obama was in Florida on Friday for the proposed launch and met with Commander Kelly and his team. He also met with Giffords.

The 14-day mission will see the crew of the Endeavour deliver the Alpha Magnetic Spectrometer (AMS) and spare parts including two S-band communications antennas, a high-pressure gas tank, additional spare parts for Dextre to the International Space Station. 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 across the country.

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