I am a happy Continental OnePass frequent flyer as they have competitive fares and many flights out of my home airport, Newark. However, I had to book an upcoming trip to Europe on British Airways.

I am looking for a U.S. airline's frequent flyer program to join to accumulate miles for this trip, and other future trips when I cannot use Continental.

Is there another U.S. airline (not Continental) that?:
(a) is a partner airline with British Airways
(b) has competitive fares
(c) has many flights out of Newark, or maybe LGA/JFK.

Thanks!