The Isle of Sark Shipping Company operates small ferries from Sark to St Peter Port, Guernsey. The service takes 45 minutes for the 9 miles (14 km) crossing. A high-speed passenger ferry is operated in summer by the French company Manche Iles Express to Jersey. A 12-passenger boat, the Lady Maris II, operates regular services to Alderney. The island is a car-free zone where the only vehicles allowed are horse-drawn vehicles, bicycles, tractors, and battery-powered buggies or motorised bicycles for elderly or disabled people. Passengers and goods arriving by ferry from Guernsey are transported from the wharf by tractor-pulled vehicles. To the dismay of residents, large tractors, which produce even more noise and dust than cars of the same size, have proliferated in recent years. There is no airport on Sark, and flight over Sark below 2400 ft is prohibited by the Air Navigation (Restriction of Flying) (Guernsey) Regulations 1985 (Guernsey 1985/21). The closest airports are Guernsey Airport and Jersey Airport. Sark lies directly in line of approach to the runway of Guernsey airport, however, and low-flying aircraft regularly fly over the island.