All aircraft are a bundle of compromises. Some designs fly well at low altitudes but are unable to sustain flight at high altitudes. Some are optimized for high altitude but fly poorly at low altitudes. Some are designed to carry heavy loads and some carry little more than a pilot. The Perlan 2 is an airplane designed to fly the most efficiently at 50,000 feet but fly acceptably at sea level and at 90,000 feet. It has 84 foot long wings, can carry two pilots, scientific instruments, life support and two safety parachutes and have the same weight as a 1967 Volkswagen Beetle.