Historical clue formulations

• Delta competitor, in brief — 2020-05-24
• Suffix with sex or text — 2019-10-06
• Delta competitor: Abbr. — 2017-07-11
• Carrier inits. — 2015-12-13
• Carrier inits. — 2013-11-10
• Founding member of the Star Alliance, for short — 2013-06-07
• An end to sex? — 2013-06-05
• Carrier whose theme is "Rhapsody in Blue": Abbr. — 2012-07-14
• Delta competitor: Abbr. — 2012-06-18
• "Fly the friendly skies" co. — 2010-03-02
• Carrier with a hub at LAX — 2009-12-02
• Delta competitor: Abbr. — 2009-10-02
• Inits. at J.F.K. — 2007-05-05
• "Friendly skies" flier: Abbr. — 2006-05-16
• Delta rival: Abbr. — 2005-06-08
• Initials at O'Hare — 2003-04-27
• TWA rival — 2000-05-02
• American rival: Abbr. — 1998-10-01