Historical clue formulations

• Former rival of Delta — 2025-04-28
• Bygone carrier whose first hub was in Pittsburgh — 2024-06-26
• Carrier name until 1997 — 2022-01-05
• Former competitor of Southwest — 2020-02-17
• TWA competitor — 2017-10-01
• Carrier name until 1997 — 2016-12-08
• Bygone carrier — 2016-08-07
• Early customer of Boeing — 2016-03-04
• Old carrier name — 2015-05-03
• Southwest alternative, for short — 2014-10-20
• TWA competitor — 2014-04-06
• Company that added four letters to its name in 1997 — 2014-02-15
• Carrier name of 1979-97 — 2013-07-17
• Carrier name until 1997 — 2013-06-12
• TWA competitor — 2012-07-08
• Former carrier name — 2011-06-19
• Pan Am competitor — 2011-05-16
• Eastern competitor — 2011-04-28
• Carrier renamed in 1997 — 2011-04-06
• Onetime TWA competitor — 2010-12-08
• Delta alternative, once — 2009-11-16
• Old carrier name — 2009-10-07
• Jetliner name until 1997 — 2008-11-26
• Aviation name until 1997 — 2007-06-14
• TWA competitor — 2006-11-06
• Name on planes, once — 2006-09-12
• Former carrier name — 2006-07-12
• Old carrier name — 2006-07-09
• Former name in flight — 2006-06-16
• Carrier once with an American flag logo — 2006-04-12
• Major company renamed in 1997 — 2005-12-30
• Carrier that acquired Piedmont — 2005-01-31
• Carrier name retired in 1997 — 2003-04-05
• Old Pan Am rival — 2002-02-26
• Carrier name until 1997 — 2001-05-03
• Carrier that bought Piedmont in the 1980's — 2000-10-15
• Company once called Allegheny — 2000-08-09
• Name on jetliners, once — 2000-01-06
• New name for Allegheny in 1979 — 1998-11-20
• Name on many planes — 1998-06-16
• Pan Am rival, formerly — 1997-10-20
• Boeing customer — 1995-07-30
• Allegheny, today — 1995-04-09
• Travel section advertiser — 1994-06-19
• Client of 16-Across — 1994-01-19