On Ebay you can buy all four movies for under $20.00:
Movie description
This program contains the complete AIRPORT disaster-film series. Films include: AIRPORT, AIRPORT 1975, AIRPORT '77, and THE CONCORDE: AIRPORT '79. Please see individual titles for complete information.
Credits
Cast: Alain Delon, Brenda Vaccaro, Burt Lancaster, Charlton Heston, Charo, Christopher Lee, Darren McGavin, Dean Martin, Eddie Albert, Efrem Zimbalist Jr., George Kennedy, Gloria Swanson, Helen Hayes, Helen Reddy, Jack Lemmon, Jacqueline Bisset, James Stewart, Jean Seberg, Joseph Cotten, Karen Black, Lee Grant, Linda Blair, Olivia de Havilland, Robert Wagner, Susan Blakely, Susan Clark
Details
Edition: Four Movies On Two DVDs