Nav Canada officials responsible for Gander Oceanic Airspace said last week they are concerned about the number of non-HF-equipped aircraft transiting their airspace. "Depending on altitude and route of flight, it is possible to traverse some portions of our area with only VHF. However, for flights outside these areas or at altitudes that do not [allow] two-way VHF contact, regulations and guidelines have been published by both Transport Canada and ICAO," the officials said. Nav Canada spokesmen said that while their organization did not write the rules, it is responsible for adhering to them. ICAO Nat doc 2.4.10 states, for example, "In controlled airspace, flights must be able to conduct two-way radio communications on required frequencies. In Gander, Shanwick, Santa Maria, Reykjavik, Sondrestrom and New York FIRs, HF radio is required in order to contact ATS units when beyond the range of VHF. Subject to prior arrangement, VHF-only flights may be made via Canada/Greenland/Iceland/Europe, provided the Shanwick OCA is avoided." Nav Canada said its ATC organization "needs to ensure that aircraft can be contacted appropriately at all times, via the approved method – HF, or VHF when in range."