[Aaron_A]

The C-38 is an Astra SPX business jet.
http://www.fas.org/man/dod-101/sys/ac/c-38.htm

The C-21 is a military version of the Learjet 35A.
http://www.fas.org/man/dod-101/sys/ac/c-21.htm

[Maximum Leader]

I thought the C-21 was a Lear, but I don't think I've ever seen an Astra business jet before. Though I have heard that the Astra is what Lockheed calls the Aurora which the Air Force may or may not fly :O)

Thanks for the links.