To avoid unforeseen traffic overload of ATC sectors in Europe the Eurocontrol Network Manager strongly expects all IFR flights that they will actually be operated at the cruising altitude filed in their flight plan. Inflight change in requested flight levels should be avoided.

Based on the recent experiences in Budapest FIR some IFR flights (particularly departing and arriving from/to LHBP) are observed planning their flights at low cruising altitudes (below 9500 feet) to avoid traffic restrictions imposed on the lower ACC sectors in Budapest CTA. HungaroControl draws the attention of operators performing such flights within Budapest FIR to the following:

• HungaroControl considers these flights being planned intentionally in uncontrolled airspace consequently they will be expected to operate at the requested altitude for the given section of the route filed in their flight plans.
• Except in an emergency, for IFR flights intentionally operating in uncontrolled airspace ATC cannot guarantee the entry into controlled airspace by approving a change in their requested flight level (especially, if traffic restrictions are in force in the ATC sectors concerned).
• Flights with cruising altitudes below 9500 feet – outside of TMAs and CTRs – will operate in uncontrolled airspace (ICAO Class G), in which traffic unknown to the appropriate ATS unit can be operating, where the responsibility for the prevention of collision solely relies on the air crews.