Answer these simple questions:
1) Are you crossing the Atlantic Ocean during your flight? If yes you are on a BusinessFirst route. If no go to the next question.
2) Are you crossing the Pacific Ocean during your flight (excluding to/from Hawaii and Guam)? If yes you are on a BusinessFirst Route. If no go to the next question.
3) Are you flying to/from Hawaii? If yes, are you flying on a wide-body plane? If yes to both you are on a BusinessFirst route. If you are on a narrow-body plane you are not on a BusinessFirst route.
4) Are you flying to/from Guam? If yes, are you flying on a wide-body plane and NOT to/from Narita (NRT)? If yes to both you are on a BusinessFirst route. If you are on a narrow-body plane or if you are flying to/from NRT you are not on a BusinessFirst route.
5) Are you flying to Peru, Argentina or Brazil on Continental metal (not Copa)? If yes you are on a BusinessFirst route. If no you are not on a BusinessFirst route.
Please note: the aircraft servicing your route may be equipped with a BusinessFirst cabin (e.g. a 777 flying IAH-EWR or a 752 flying EWR-SDQ). However, since the flight operates in a non-BusinessFirst market elite members are still eligible for their complimentary upgrade.
Should your itinerary have a combination of BF marketed and non-BF marketed flights you will still be eligible for a EUA on the non-BF marketed flights. Here are a few brief examples:
Example 1: You booked a ticket to go from PDX to TXL via EWR. The PDX-EWR flight (with domestic First Class service) would be eligible for a EUA but the EWR-TXL one (with BusinessFirst service) would not.
Example 2: You booked a ticket to go from FRA to SXM via EWR. You would not be eligible for an upgrade on the FRA-EWR flight (with BusinessFirst service) but would be eligible for a EUA on the EWR-SXM flight (with International Business service).
The CO website is known for being slightly "confused" as to whether a route is BF service or not since some BF-equipped planes are operated on non-BF routes. If your flight is operated by a 767 or 777 and is not an EWR-IAH routing (or other lower-48 flight, though there are none regularly scheduled) it is almost certainly BF-marketed. The only current exception to this is the GUM-NRT flights operated on 767s by CO Micronesia. The 757-200s make things a bit more confusing, but the general answer for those flights is that it is only a BF flight if it is between EWR and a European destination or Lima, Peru. No other 752 flights are currently BF marketed and therefore they are all EUA-eligible. This includes any LAX-HNL flights. Now that the 73E is also working that route the flights are EUA-able regardles of which equipment operates them.