....
'Unlike the Challenger/asbestos claim, however, this one seems to actually have some basis in fact. A 1999 NASA press release on the matter has been yanked off the web, but is still available thanks to Google. Here's the full text:

"DRYDEN F-15B SUPPORTS SHUTTLE EXTERNAL TANK INSULATION TESTS January 28, 1999 Release: 99-1 Flight tests at the NASA Dryden Flight Research Center, Edwards, Calif., recently demonstrated that a new type of insulation foam used on the Space Shuttle's giant external tank remains intact under some of the dynamic environments seen during the initial stage of the Shuttle's ascent. Mimicking a Space Shuttle launch profile, an F-15B research aircraft based at NASA Dryden flew a series of missions to evaluate the dynamic response characteristics of the new insulation material. The Shuttle External Tank
Experiment involved six research flights over a two-week period by Dryden's F-15B in partnership with NASA's Marshall Space Flight Center, Huntsville, Ala., and the Michoud Assembly Facility near New Orleans, La.

"This experiment was a perfect example of the versatility of the F-15B and its Flight Test Fixture," said Dave Richwine, Dryden's F-15B project
manager. "It shows how we can customize our capability for any particular experiment's requirements." '

From:
CCNET