The use of tablets and iPads in-flight is up 15%, with more than one in four travellers now calling theirs a carry-on essential, according to the April 2012 release of TripAdvisor's annual air travel poll, which surveyed more than 1,000 US travellers.

Much of the reason for that increased usage is increased sales: Tablet sales worldwide are expected to nearly double in 2012, then increase by 50% between 2012 and 2013, and double again between 2013 and 2016, according to Gartner's "Forecast: Media Tablets by Operating System Worldwide, 2010-2016, 1Q12 Update," released in April 2012.