1) You can get upgraded internationally even if you used points to book on Delta. We were upgraded to first class on our flight from JFK to Barcelona despite all my inquiries and being told I was not eligible. I paid 220,000 points for two coach seats. It was another 230,000 points to upgrade to first class. We ended up getting the upgrade for free. So you never know.
2) TSA Pre-check will not work for international flights. I thought I would be ok for my flight from Boston to JFK. No go. I did apply for international Clear, but I’m still in the process.
3) Your position on the upgrade list when flying a “partner” airline is usually all the way on the bottom. Despite my status with Delta, I flew Alaska air from Boston to Seattle and was #19 out of 19 on the upgrade list. I inquired with the gate agent, as I found it unlikely that all these people had flown over 120,000 miles thus far this year. I was told Alaska members are listed first, then partner airline members second. I did get 2500 MQM points for the trip, but no upgrade either way.
4) TSA pre-check only works for your primary airline. Another disappointing discovery. I received pre-check from Delta…and evidently it is only good when flying Delta domestically.
5) Finally, when returning from an international flight at JFK, you have to go through security again. We never went outside the terminal. You pick up your luggage, go through customs and then drop off your luggage on the other side for your connecting flight. The tricky thing was another security station right there. We had bought duty free on the flight home, so we had bottles of vodka in our backpack. No one mentioned we had to go through security again. Fortunately our bags had not gone down the belt yet, so we were able to put the bottles in our checked luggage and return to the security line. And oh, no pre-check here or first class lines for that matter.