US Airways has ended their "
buy up to preferred" program when they joined oneworld.
AA enforces a four-segment minimum rule now (they had this for a long time but it wasn't enforced up to earlier this year).
UL and RJ have comparably low limits for status qualification, but high own metal segment minimum thresholds:
with UL's Fly Smiles you'll qualify for Emerald after 60k 'tier miles', but half of that needs to be on UL.
RJ's program lets you qualify for top tier status after 55k miles, but requires a minimum of 12 (or even 20 - there's contradicting info in their T&Cs) segments on RJ metal.
LAN still has that shortcut to Emerald status if you fly with them in premium cabins, modified a bit since merging with TAM:
Fly 80,000 kms with LAN, TAM or oneworld, with a minimum of 8 medium or long-haul legs with LAN or TAM in Business Class. As they define "medium-haul" as everything international over 1,600 kms in length, this could be useful for anyone flying around South America.
Otherwise, the program lets you qualify for Comodoro (OWE) after 150,000 kms the regular way - that's 93,225 miles and a bit less than the 100k miles most other programs require.