Back in 1972, the UN established June 5 as World Environment Day in an effort to raise awareness of the various harmful ways humans affect the planet. This year, air pollution was the theme. Airlines are keenly aware of their role in damaging the atmosphere, given that they account for about 2% of annual global carbon emissions. So it’s probably not a surprise that, this month, a few of them are showing how they’re trying to shrink their footprint. One of them had an experiment lined up for Wednesday morning, the very day chosen by the UN: United scheduled a flight to California that aimed to go all green. The world’s second-largest airline planned to reduce cabin waste to zero, while flying on a biofuel mixture and “erasing” the remaining emissions with carbon offsets—all on a one-off flight from Chicago to Los Angeles. The company called the trip by one of its Boeing 737-900ERs a “flight for the planet,” asserting that it’s the first time an airline has ever combined all three efforts on a single commercial flight. When it comes to garbage at least, airlines would like to see their flights produce zero waste someday, migrating to compostable and fully recyclable serviceware such as cups and food wrappers. United Continental said its average flight generates 65 pounds of trash. On the Wednesday trip, the airline got it down to 14 pounds, all of which was brought aboard by passengers, the carrier said. “Zero-waste produced from United, so we met our goal,” spokesman Charles Hobart proclaimed. Part of the effort included giving everyone a plated meal with fully recyclable or compostable dishes and utensils, instead of the usual for-sale snack boxes.<br/>