Heading on your honeymoon or travelling for a big birthday? It may have crossed your mind to ask for a free flight upgrade. But could it really result in you sipping Champagne in a sky-high armchair or will you simply get an eye roll from the airline staff? Frequent flyers from Reddit’s travel community have weighed in on the topic, sharing real-life experiences and insights on how flight upgrades work. To back it up, Euronews Travel spoke to some of Europe’s biggest international airlines to find out how upgrades are assigned. Here’s what we found out. Are free upgrades at the gate just in th…