Email will be available on all domestic flights in North America before the end of next year, although services elsewhere in the world will take two to three years to become widespread according to the chief executive officer of Tenzing Communications, which provides technology and services for in-flight messaging.

United announced a deal with Tenzing last week to provide email on approximately 400 of its North American domestic flights by the end of this year.

Tenzing will confirm similar deals with other airlines in the coming months said Alan McGinnis, chief executive officer of the company, who was in town for the Paris Air Show last week. All domestic flights in North America will be equipped for email by the end of next year, he predicted.

Passengers can already send email on some United flights by connecting their laptops to its existing JetConnect service. But sending email that way is prohibitively expensive, and JetConnect wasn't designed for transmitting data, according to McGinnis. JetConnect with Email, the enhanced service being rolled out by United, is supposed to address those issues.

Verizon's network allows for a data connection speed of 9.6Kbps (kilobits per second) in the States. Tenzing's main rival is Boeing's Connexion, which lets passengers surf the web via a high-speed broadband connection as well as send and receive email. Lufthansa said last month that it would equip its fleet of about 80 long-haul aircraft with the service beginning early next year, while BA has recently completed a successful trial of the service.

McGinnis admitted that broadband services will dominate the skies eventually, but he argued that Tenzing's service is currently the best option for cash-starved airlines because it only needs a software upgrade, making it relatively cheap to implement. By comparison, Connexion by Boeing requires airlines to fit their planes with new equipment to provide the broadband connection.

Tenzing hopes to evolve its service to higher speeds over time by piggybacking on top of new, faster communications equipment that it expects will be fitted to aircraft as standard in the near future.

Services outside the US will likely take longer to implement, said McGinnis, because of the time involved in brokering deals, regulatory issues and other concerns.