Eiffel agreed to take on the project, provided he could build on a rock foundation if found at a depth of less than below the ice. In 1891, the Swiss surveyor Imfeld dug two horizontal tunnels below the ice summit but found nothing solid. Consequently, the Eiffel project was abandoned. Despite this, the observatory was built in 1893. During the cold wave of January 1893, a temperature of was recorded on Mont Blanc, being the lowest ever recorded there. Levers attached to the ice supported the observatory. This worked to some extent until 1906, when the building started leaning heavily. The movement of the levers corrected the lean slightly, but three years later (two years after Janssen's death), a crevasse started opening under the observatory. It was abandoned. Eventually the building fell, and only the tower could be saved in extremis. Air crashes The mountain was the scene of two fatal air crashes; Air India Flight 245 in 1950 and Air India Flight 101 in 1966. Both planes were approaching Geneva Airport and the pilots miscalculated their descent; 48 and 117 people, respectively, died. The latter passengers included nuclear scientist Homi J. Bhabha, known as the "father" of India's nuclear programme. Tunnel In 1946, a drilling project was initiated to carve a tunnel through the mountain. The Mont Blanc tunnel would connect Chamonix, France, and Courmayeur, Italy, and become one of the major transalpine transport routes between the two countries. In 1965, the tunnel opened to vehicle traffic with a length of . 1999 disaster In 1999, a transport truck caught fire in the tunnel beneath the mountain. In total, 39 people were killed when the fire raged out of control. The tunnel was renovated in the aftermath to increase driver safety. Renovations include computerised detection equipment, extra security bays, a parallel escape shaft, and a fire station in the middle of the tunnel. The escape shafts also have clean air flowing through them via vents. Any people in the security bays now have live video contact to communicate with the control centre. A remote site for cargo safety inspection was created on each side: Aosta in Italy and Passy-Le Fayet in France. Here all trucks are inspected before entering the tunnel. These remote sites are also used as staging areas to control commercial traffic during peak hours. The renovated tunnel reopened three years after the disaster. Elevation The summit