Simon Calder: A twenty-minute call could cost as much as your ticket

As the the low-cost airline industry plunges into its gloomiest-ever winter, the quest for "ancillaries" is intensifying. Average air fares in Europe are set to fall even further during the next few months. With airlines making a loss on the tickets, they are ever more desperate to find other revenue streams. Ryanair's experiment may earn it useful commission – but in-flight phone calls could cost its customers dearly.

The exact cost of making or receiving a call is hard to pin down.

Ryanair, which is Europe's largest no-frills carrier, says "normal international roaming rates" will apply. Now, at ground level, charges for international calls within Europe are capped at 38p per minute for outgoing calls, 19p for incoming. But calls to and from commercial transport – ships or aircraft – are uncapped, because the capital and running costs tend to be much higher.

Ryanair's inflight phone service will be operated by OnAir, a joint-venture communications company owned by Airbus and the airlines' telecom provider, Sita. OnAir will charge the passenger's mobile network a wholesale rate of between £2 and £3 per minute. (Of that, less than £1 is expected to go to Ryanair.) Curiously, O2 – one of the service providers involved in the Ryanair launch – says it will charge no more than £1.99 per minute for incoming or outgoing calls. Even at that favourable rate, a 20-minute call would end up costing as much as the average Ryanair fare.

The move carries risks for Ryanair. Survey after survey suggests that most passengers are against mobile phones on planes; British Airways says its customers are overwhelmingly opposed to the concept.

BA could pick up business at the expense of Ryanair. But Emirates, which has been offering in-flight mobile use for six months, reports extremely high use within the Middle East and on daylight flights from Dubai to Europe, yet has experienced no phone-related "air-rage" incidents. But only a small proportion of its fleet is equipped for mobile use, and Ryanair will initially fit out only8 per cent of its planes.

If you cannot bear to be out of contact for a couple of hours, the best advice is to stay at home.