Most large airlines are members of an alliance which means you can earn and redeem miles for one airline on any of the other carriers in its group. Star Alliance, Skyteam and oneworld are the main alliance groups. My advice is to pick one in each and only earn on those three airlines. Every time you fly check which group you will be flying with and request to earn miles on your chosen airline. When you accrue enough miles for free travel, you can redeem with your choice or any of its partners.

For example, I choose American as my airline in the oneworld alliance. When I fly Lan, another oneworld member, I tell them I’d like to earn American miles. When I have enough miles for a free ticket, I can redeem them on American, Lan or any of the other oneworld carriers.

Here are the airlines included in each alliance:

Star Alliance:

Adria, Aegean, Air Canada, Air China, Air New Zealand, ANA, Asiana Airlines, Austrian, Blue1, BMI, Brussels Airlines, Croatia Airlines, Egyptair, Ethiopian Airlines, LOT Polish Airlines, Lufthansa, Scandinavian Airlines, Singapore Airlines, South African Airways, Spanair, Swiss, TAM, TAP Portugal, Thai, Turkish Airlines, United, US Airways

Skyteam:

Aeroflot, AeroMexico, Alitalia, Air France, KLM, China Airlines, China Eastern, China Southern, Delta, Korean Air, Czech Airlines, Air Europa, Kenya Airways, TAROM, Vietnam Airlines

oneworld:

American Airlines, British Airways, Lan, Qantas, Royal Jordanian, Finnair, Iberia, Malev, Mexicana, Japan Airlines, Cathay Pacific, S7 Airlines