I recently booked a flight on CO, routing EWR-DTW on Jan. 7th, 2011, returning on the 9th. The outbound flights on the 7th were all operated on XJ metal, with XJ flight numbers. When it came to choose the return flight, I noticed that out of 5 options for return flights, 3 of them were being flown on UAX (operated by Shuttle America) E-170's. but the flight numbers for the UAX operated flights were as follows, 1285, 1283, 1284. These flight numbers seem like they would be assigned to mainline CO ops, not express flights.
Are CO and UA merging their express flying? Will the crew on the return flight say "Welcome aboard CO 1284"? And will the flight arrive at the United gates at A1 in EWR? or the CO gates in A2 or even the mainline gates in C? Any info on this would be good, since I haven't heard anything about merged regional flying between the two airlines.