Orange County (SNA) (Disneyland) — Long Beach (LGB), Ontario (ONT) + LAX
Palm Springs — Ontario (ONT)
San Antonio — Austin (AUS)
San Francisco — Oakland (OAK)
Also, San Jose (SJC) - an hour away outside of rush hour. Transfers without a car can be either time consuming or expensive.
Santa Fe — Albuquerque (ABQ - usually much cheaper)
Toronto — Billy Bishop (YTZ - nearly downtown), Buffalo (BUF), Hamilton, ON (YHM)
Tucson — Phoenix (PHX)
Vancouver, BC — Bellingham WA (BLI - if will rent car), Seattle (SEA)
Washington, DC (DCA) — Baltimore (BWI), Dulles (IAD)
Who wants to drive 3 hours or take an airporter bus from Vancouver to Seattle, which can take longer with customs delays at the border?
Well, high Canadian airfare taxes and high fares fostered by less competition are a powerful motivator.
Alternative airports NYC
Even though LaGuardia Airport (LGA) in New York City sits closer to Midtown Manhattan, Newark (EWR) and JFK airports are often cheaper. Although served by airporter bus transfers, LaGuardia lacks the convenient public transit options the others have.
Alternative airports work around the world. For example, London has 5 busy airports: well-known Gatwick (LGW) and Heathrow (LHR), but also London City (LCY), Luton (LTN), and Stansted (STN).
Paris has 3 choices; Barcelona 2.
With high-speed rail access found at many European airports, you can, as an example, land in Brussels and be in Amsterdam in under 2 hours by train. Worth doing if you save 100s of dollars.