Well...for the price, not many complaints, BUT. Couldn't do OLCI as it wanted visa to enter for my way. The way the agent handled the check in at PRG was totally unprofessional (speaking loudly on the phone, telling someone our passport numbers, birthdays, names to check if we have ESTA...). No lounge at PRG as ATR segments are economy with no service.
Did get hotel, called Air Serbia on the day of travel, they told me it is too late but they will make a note and I have to contact Air Serbia once we land.
Lounge at BEG is everything you need from showers to great food and well stocked bar.
BEG-JFK was probably the weirdest J flight of my life as I don't get the dining concept. On a 10 hour day flight departing at 7am I would appreciate small snack for breakfast and full lunch before landing but no, we got three-course breakfast and snack selection was very disappointing. Even we were first to deboard as J pax the crew let Y to get in front of us. The crew was like hey we are from Etihad working for Air Serbia thus we don't feel like we need to go beyond. They really didn't.
Check in at JFK opens 3 hours and a few minutes before departure, pax can use J line for security screening. Wingtip lounge is a joke but has very decent selection of beers. The flight back to Europe was way better - good dinner and a few hours of solid sleep as the flight is longer than usual hops over to LHR, AMS or CDG. Same crew but as you "don't need them" on a red eye, no complaints this time.
BEG-JFK 8 empty seats in J and 2 pax (elderly couple) upgraded on board (probably they got to know someone from CC). Y almost 100%.
JFK-BEG 1 empty seats in J and Y again almost totally full.
Well, for the price it was great as I took my dad and it was his only 2nd time flying intl business so he loved it. Personally I wouldn't go for it again even for such a price.
