For potential comparison with AC's SE and Elite, TWA's top two tiers go:

Platinum - at least $20,000 US in published fares, 100,000 actual miles, or 20 or more transatlantic segments during a calendar year.
Benefits include:
unlimited upgrades.
Domestic upgrades confirmed at time of booking on Y or B fare; 100 hours prior to departure any other TWA published fare.
international upgrades within 100 hours of departure when purchasing a Y fare; $400 from B fares
no blackout date restrictions and no seat limitations on awards.
1000-Mile Minimum for every flight
100% mileage bonus based on the actual number of miles flown
free Ambassadors Club Access

Elite1 - at least $10,000 US in published fares,* 50,000 actual miles or 10 Transatlantic segments during a calendar year
Benefits include:
Unlimited complimentary domestic upgrades
minimum of 1,000 miles/flight.
50% mileage bonus based on the actual number of miles flown