Harmony: that is what the European Commission professed to promulgate this week. The decision on "harmonised conditions of spectrum use for the operations of mobile communication services on aircraft" promises to enhance "quality of life". But Brussels' announcement of the freedom to roam, telephonically, at 30,000 feet spells only discord.

At present, the rule is clear: you should never use a mobile phone while in flight. Among frequent flyers, all sorts of reasons are cited to explain the ban. Some assert that it is a conspiracy by the airlines to persuade us to use their expensive inflight links. For years, many US carriers have offered telephones, installed in cabins, that provide satellite communication with the ground for around £3 a minute. Others ascribe assorted aviation disasters to passengers using mobile phones in flight: the signals, they say, override the pilots' controls.

The reality, as far as I can tell, is as follows. Suppose you are aboard an aircraft that is flying over territory peppered with mobile-phone base stations. There is no technical obstacle to your making and receiving calls. Indeed, many of the passengers aboard the hi-jacked Boeings on 11 September 2001 said goodbye to their loved ones by mobile phone, in circumstances when any possible interference with aircraft systems was irrelevant.

However, there is a very good reason why passengers should currently switch off their phones between departure and arrival. Mobiles are designed to send out signals seeking a base station. When they cannot immediately locate one, they boost the strength of the signal and try again. This radiation can get so intense that it may give false readings on the instruments on the flight deck. If there is one thing upon which pilots and passengers can agree, it is that the captain and first officer should have the best information possible.

The solution is to turn the whole aircraft into a base station for mobile telephony – a development that some airlines hope will turn their planes into profitable phone booths. The system will work like this. Once the aircraft is above 10,000 feet, an announcement will be made that you can switch on your phone. (The height limit is standard for all forms of electronic equipment, to avoid any risk of interference in the critical stages of the flight.) The screen on your phone should show the operator as Air France, BMI or Ryanair – three of the leading airlines that say they are keen to start the "service" as soon as possible. Effectively, you are in a foreign country (or, in the case of Ryanair, another planet), and the telecom provider can charge what it likes.

Ryanair says it will launch the service aboard 20 of its Boeing 737s in June, but won't reveal how much it will charge to make or receive calls, saying only that rates will be "in line with international roaming rates".

I reckon the price will be around the £2-plus-per- minute level currently charged by some ferry lines, rather than the 38p-per-minute limit imposed in the EU for calls made from ground level. And I also predict a riot, or at least a row, when the service begins.

Nine out of 10 airline passengers in Europe, says the Commission, carry mobiles. That means an average of 170 aboard a full Ryanair flight – a terrifying prospect. Now, no one can claim that the average no-frills flight is a haven of tranquillity, but how much worse it will be when the passenger next to you starts a loud conversation – and they are guaranteed to be deafening, because of the high ambient noise level – a cacophony that will be exacerbated by the inevitable random refrain of ridiculous ringtones.