Correction: An earlier version of this editorial incorrectly stated that April 12 would mark the 30th anniversary of the launch of the shuttle Discovery. In fact, the Columbia was the shuttle launched on that day in 1981. The version below has been corrected.

APRIL 12 MARKS the 50th anniversary of human spaceflight and the 30th anniversary of the launch of the shuttle Discovery. This is the day that NASA has said it will announce who will get to house the three retiring space shuttles.

Moving, cleaning and preparing the shuttles for display will cost slightly more than $28 million apiece and require extensive precautions — the vessels are too fragile to travel in the rain and require two 747 jets to carry them. These funds are to be supplied by the recipient institutions in exchange for becoming the orbiters’ final destinations.

This should be an apolitical process. But, so far, it has not been.

First a provision requiring the locations selected for retired shuttles to be historically connected with the shuttle program was stricken from the NASA Authorization Act — making many more destinations eligible. Then$14 million was included in President Obama’s 2012 budget request to defray the initial transportation and cleaning costs for a Dayton, Ohio facility that has applied to house one of the shuttles — when no official decision has yet been made.

No matter what, NASA will have to disappoint some applicants. Currently, 21 sites are in contention to house only three shuttles. (There are four shuttles in all; since 2008, it has been understood that the Discovery would replace the Enterprise, a test model, at the Smithsonian’s Steven F. Udvar-Hazy Center, with the other three going to museums across the country.) That’s a powerful argument for making the criteria for housing the shuttle clear upfront. The original requirements were sensible — with so few shuttles to allocate, giving precedence to applicants with connections to the shuttle program is not unreasonable.

So far, the selection process has been shrouded in mystery — no doubt from a desire to avoid pressure from the dozens of “shuttle-boosting” campaigns now making headlines. But this isolation has reached the point that it is hard to tell on what basis the decision is being made, with at least one museum reporting no contact from NASA since last year’s submission of proposals.

The shuttle offered an opportunity for us to gaze up and forget our divisions, inspired by the work that the brave men and women aboard it were able to achieve. We hope that bringing it down to Earth will not return us to the gravitational pull of particular interests. It may be difficult to keep politics out of this process. But the least we can ask for is a level playing field for the potential recipient sites and transparency in how the decision is reached. The shuttles are honors to be bestowed, not prizes to be bought.