The most likely passenger to score a free upgrade? A well-dressed man in his 30s, who is traveling solo.

Travel search engine Skyscanner quizzed 400 international hotel workers to draw up a list of the top ten unusual grumbles and diva-like demands.

Holographic airport staff, zen airports with waterfalls, yoga classes and no more check-in desks are among some of the predictions made in that report.

Dutch airline KLM has been ranked the No. 1 airline in Europe for its long-haul, in-flight dining program by users of British-based travel booking site Skyscanner.

Paris Charles de Gaulle, the second busiest airport in Europe, is the rudest in the region, while Copenhagen Airport features as the friendliest.

Scotland-based flight comparison site Skyscanner said its poll indicates airline passengers consider 6A to be the best seat on a standard aircraft.