Airlines were investigating why windshields on at least 13 planes cracked at Denver International Airport as winds of up to 100 mph whipped through the foothills in Colorado.Interstate 70, the main east-west route through the state, was closed again Saturday morning near the Eisenhower tunnel so highway crews could conduct avalanche control work. U.S. 40 over Berthoud Pass, where an avalanche last month buried two cars, was also closed due to the threat of avalanches. Many skiers heading to Grand County were waiting in Empire, Colo., for the pass to reopen.U.S. 285 between Kenosha Pass, west of Grant, and Fairplay was also closed Saturday morning due to adverse weather conditions.The storm system that brought nearly a foot of fresh powder to ski resorts, was expected to move out of the state Saturday.Meanwhile, SkyWest Airlines reported cracked windshields on eight planes that were taking off or landing between 1:30 and 3:30 p.m. Friday as winds were gusting up to 50 mph, spokeswoman Marissa Snow said. One plane suffered a cracked windshield while it was airborne."Only the outermost layer was affected," Snow said of the windshields, which are made from multiple layers of glass.SkyWest, a regional carrier for United Airlines, said the planes involved were the Embraer EMB120 Brasilia and Bombardier Canadair Regional Jet, though she did not immediately have numbers.Two Frontier Airlines Airbus planes had their windshields crack while airborne, while two other windshields cracked while at the gate, airline spokesman Joe Hodas said.In all instances the planes returned to the airport and/or made it to the gate safely. No emergencies were declared and no injuries were reported.Hodas said it was unclear whether the high winds were to blame."It's not exactly unusual weather for Denver," Hodas said. "We don't know what it is... It's kind of a mystery at this point."Spokesman Steve Snyder said windshields cracked on several different makes and models of airplanes from several airlines, though he did not immediately know which and how many. None of the pilots reported flying debris, Snyder said."Everybody is fairly baffled by it," Snyder said.At least 55 flights were canceled by the winds and some flights were diverted to Grand Junction, Wichita, and Colorado Springs.While the snow promised prime skiing conditions for the holiday weekend, Aspen Mountain was forced to close a gondola and lift by noon Friday as 62 mph gusts hit the mountain and wind speeds averaged between 25 and 30 mph. Other lifts closed later in the afternoon, with disappointed skiers getting refunds."The wind kicked up everything from broken branches to pine cones," Steven Sadler, a visitor from Los Angeles who skied Aspen Mountain Friday told The Aspen Times."I can't recall anything like this in the last few years," Aspen Skiing Co. spokesman Jeff Hanle told the Times. "Most guests know the weather is beyond our control."Along the Front Range, where 3.8 million of Colorado residents live, National Weather Service technician Carl Burroughs described the wind as "like a river running through the mountains.""The wind does the same thing through the canyons here," he said.A gust of 101 mph was recorded south of Boulder, Colo., about 30 miles northwest of Denver at about 2:30 a.m. Friday.In southern Wyoming, parts of Interstate 80 were closed between Cheyenne and Laramie because of windblown snow driven by gusts over 50 mph and icy patches.Just before I-80 was closed in the morning, the driver and a passenger in a tractor-trailer were killed in a crash at Laramie, according to Wyoming Highway Patrol Lt. Troy McLees.Later in the day, five tractor-trailers crashed into one another just west of Laramie. McLees said at least one person was taken to a hospital from that crash.In Colorado, high wind advisories were issued for hundreds of miles of highways. Two short stretches of Interstate 70 in the mountains west of Denver had to close because of high winds and blowing snow, and a 60-mile stretch between east Vail and west of Evergreen was temporarily closed. U.S. 6 over Loveland Pass and U.S. 40 over Berthoud Pass and between Kremmling and Steamboat Springs were closed because of avalanche danger, and U.S. 285 was closed over Kenosha Pass for a time.The American Red Cross Mile High Chapter set up shelters in Granby, Fraser and Silverthorne for stranded travelers.The Winter Park ski area shut down around noon Friday. Resort spokesman Matt Sugar said high winds toppled trees and created unsafe conditions for skiers.A Red Cross shelter accommodated day visitors trapped when CDOT closed Berthoud Pass, and the Ski Train, which runs between Winter Park and Denver, loaded more than 200 children stranded at the resort when their buses couldn't get over the pass."We are just so grateful to the Ski Train for really helping us out with this," Sugar said. The resort and train officials made sure the children had transportation home from Denver's Union Station, he said.By midday, high winds had moved into the Eastern Plains, with gusts of 48 mph reported in Greeley and 46 mph in Limon, 80 miles southeast of Denver.Burroughs said the position of the high-altitude jet stream combined with a high pressure system spilling into a low-pressure area was producing the strong winds.Such blasts are not unusual for this time of year along the Rockies.Colorado's highest recorded wind gust came in at 201 mph atop 14,259-foot Longs Peak in 1981 Rocky Mountain National Park. In 1971, the city of Boulder recorded a wind gust at 147 mph.