What are the worst airlines you have flown? Mine would be Xiangjang airlines, based in Urumqi China, for the old Tupolov aircraft with the ceiling panels that were falling out and the seat back tray that folded down enough to hit me in the chest. Air Nuigini (not so fondly called Air Agony) was just horrible to fly in and out of Port Moresby on. Or Air Mexicana with the clogged toilets leaving Caracus and the flight attendants that kept crossing themselves on landing.
I flew with United Airlines from Narita to Bangkok (and back). They were the worst airline I've ever flown with. The food was grim, the flight attendants were scary and the seats were pretty unbearable. I will never fly with them again. And this is saying something, considering I've flown with Easyjet a few times!
In Latin America, TACA. It's based in San Salvador, San Jose and Lima. To go from one place to another you either have to do a 5 hour layover at San Jose, CR (The airport is BOOOOOOOOOOORING... NO DUTY FREE STORES, NO NOTHING), or wake up like at 3 am to catch a flight that connects in San Salvador. Service is bad, flights never leave on schedule. HORRIBLE airline!!! Copa Airlines is the best Latin American airline!!!