iPhone and Blackberry obsessed travellers are increasingly relying on e-services from airlines to get them to their destination.

Ease and efficiency of transactions - from booking through to check-in - are important for business and leisure travellers alike, and Cheapflights.co.uk, the UK’s leading flight comparison website, has compiled a guide to e-services on most of the world’s leading airlines.

“I take advantage of e-services wherever I can,” says Francesca Ecsery, Global Sales Director of Cheapflights. “For the savvy traveller, it’s the quickest, most efficient method not only for finding the best deals but also for booking them, when arriving at the airport for check-in and planning extras on your trip. Most airlines offer online booking and check-in services, but there are a wealth of other niche services allowing holidaymakers to get on with their holiday with ease and minimum fuss.”

Cheapflights.co.uk’s latest tips page outlines 21 of the world’s top airlines, comparing five key online services including booking, online and mobile check-in, refunds and car rental.

Only four of the 20 global airlines researched offer all five areas – BMI, British Airways, Emirates and Singapore Airlines. The three US flagship carriers – American Airlines, Continental Airlines and Northwest Airlines – also offer all five online options but their mobile check-in option is only valid for the US.

A relative newcomer to the world of mobile check-in is budget airline easyJet, which will offer the service from October 2009.

Most services across all airlines are offered free of charge, with the exception of online refunds, where four airlines carry a fee.