difficult weather. Cross-country flights are allowed when they have sufficient experience to find sources of lift away from their home airfield, to navigate, and to select and land in a field if necessary. In most countries pilots must take a written examination on the regulations, navigation, use of the radio, weather, principles of flight and human factors. Proposals are being made to standardise the training requirements across European countries. In addition to the regulation of pilots, gliders are inspected annually and after exceeding predetermined flight times. Maximum and minimum payloads are also defined for each glider. Because most gliders are designed to the same specifications of safety, the upper weight limit for a pilot, after allowing for a parachute, is usually . There is also a limit, 193 centimetres (6 ft 4 in), on the tallest pilots who can safely fit into a typical glider's cockpit. Challenges for the gliding movement According to the FAI President, gliding as a sport faces challenges in the years ahead. These include: Time pressures on participants: gliding typically takes whole days that many people today find harder to devote. As a result, the average age of glider pilots is increasing. In some countries, the need for more land for housing is threatening small airfields. These airfields may also be used for other general aviation activities, and the addition of gliding may be difficult to accommodate. This can limit the number of available airfields and so it can require longer drives to reach them. Airspace: in many European countries, the growth of civil aviation is reducing the amount of uncontrolled airspace. In the U.S. new security requirements, and the growth of controlled airspace around cities, has also had some impact on where to fly. Competition from other activities: there is now a greater variety of similar sports such as hang gliding and paragliding that may attract potential glider pilots. Lack of publicity: without coverage by television or popular publications, many people are unaware that gliding is even a sport. Without this knowledge the public may have a poor understanding of how flying without an engine is possible and safe. Increasing costs: due to higher costs of fuel and insurance, and due to greater regulation requiring equipment such as new radios, or in some cases transponders, gliding costs have increased, although without the continuous use of engines and fuel, they are still considerably lower than traditional