Francisco route, and was replaced in 1965 with "Fly the Friendly Skies", which was in use until 1996 in its first iteration. The "It's time to fly" slogan was created in 2004. After the merger of United and Continental in October 2010, the slogan changed to "Let's fly together" until September 2013, when United announced a return of the "Fly the Friendly Skies" slogan in an ad campaign to start the following day. The resurrected slogan would be accompanied by the 1924 George Gershwin song "Rhapsody in Blue" as its theme song, and a voiceover provided by Matt Damon. United had licensed its theme song, "Rhapsody in Blue", from Gershwin's estate for in 1976. "Rhapsody" would have entered the public domain in 2000, but the Copyright Term Extension Act of 1998 extended its copyright another 20 years until January 1, 2020, when it officially entered on the Public Domain. United announced that it would continue to use "Rhapsody in Blue" as its theme song following the merger with Continental. Environmental initiatives Because over 98 percent of United's greenhouse gas emissions are from jet fuel, its environmental strategy has focused on operational fuel efficiency initiatives and investments in sustainably produced, low-carbon alternative fuels. On August 23, 2011, United Continental Holdings, Inc., announced a conversion to paperless flight decks and projected that by the end of the year, 11,000 iPads will have been deployed to all United and Continental pilots. Each iPad, which weighs less than , will replace approximately of paper operating manuals, navigation charts, reference handbooks, flight checklists, logbooks, and weather information. The green benefits include reductions in paper use, printing, and fuel consumption. On November 7, 2011, United flew the world's first commercial aviation flight on a microbially-derived biofuel. The aircraft was fueled with 40 percent Solajet, which is Solazyme's algae-derived renewable jet fuel, and 60 percent petroleum-derived jet fuel. This flight was operated by the Eco-Skies Boeing 737-800 aircraft from Houston to Chicago-O'Hare. On January 15, 2013, Aviation Partners Boeing (APB), a joint venture between Aviation Partners Inc. and Boeing, announced that United had agreed to replace the Blended Winglets on its Boeing Next Generation 737 aircraft with APB's Split Scimitar Winglet (SSW), significantly reducing drag. Once the SSWs are installed, it is estimated that APB's winglet technology will save United more than $250 million annually in fuel costs. On June 30, 2015, United invested US$30 million in