Solar Impulse 2 pilot Andre Borschberg (L) confers with Bob Stojanovic (R) of ABB Group - Automation and Power Technologies Director of Microgrids, during a press conference at Kalealoa Airport in Kapolei, Hawaii on April 15, 2016. The Solar Impulse 2 sun-powered plane is set to resume its record-breaking flight around the world within days, leaving Hawaii when weather permits. / AFP PHOTO / Eugene TannerEUGENE TANNER/AFP/Getty Images

People stroll under blooming cherry trees in Kungstradgarden park in Stockholm, Sweden, on April 15, 2016. Weather forecasts predict unsettled weather conditions with about 10 degrees Celcius in Stockholm during the weekend. / AFP PHOTO / TT News Agency / Henrik MONTGOMERY / Sweden OUTHENRIK MONTGOMERY/AFP/Getty Images

Visitors take a selfie with blooming cherry trees in the background in Kungstradgarden park in Stockholm, Sweden, on April 15, 2016. Weather forecasts predict unsettled weather conditions with about 10 degrees Celcius in Stockholm during the weekend. / AFP PHOTO / TT NEWS AGENCY / Henrik MONTGOMERY / Sweden OUTHENRIK MONTGOMERY/AFP/Getty Images

US President Barack Obama holds a homemade spacecraft that was attached to a weather balloon and launched 78,000 feet up into the atmosphere by 11-year-old Rebecca Yeung (L) and 9-year-old Kimberly Yeung (R) as he tours the 2016 White House Science Fair in the East Room at the White House in Washington, DC, April 13, 2016. / AFP PHOTO / SAUL LOEBSAUL LOEB/AFP/Getty Images

US President Barack Obama looks at a homemade spacecraft that was attached to a weather balloon and launched 78,000 feet up into the atmosphere by 11-year-old Rebecca Yeung (C) and 9-year-old Kimberly Yeung (L) as he tours the 2016 White House Science Fair in the East Room at the White House in Washington, DC, April 13, 2016. / AFP PHOTO / SAUL LOEBSAUL LOEB/AFP/Getty Images

US President Barack Obama looks at a homemade spacecraft that was attached to a weather balloon and launched 78,000 feet up into the atmosphere by 11-year-old Rebecca Yeung (C) and 9-year-old Kimberly Yeung (L) as he tours the 2016 White House Science Fair in the East Room at the White House in Washington, DC, April 13, 2016. / AFP PHOTO / SAUL LOEBSAUL LOEB/AFP/Getty Images

US President Barack Obama holds a homemade spacecraft that was attached to a weather balloon and launched 78,000 feet up into the atmosphere by 11-year-old Rebecca Yeung (L) and 9-year-old Kimberly Yeung (R) as he tours the 2016 White House Science Fair in the East Room at the White House in Washington, DC, April 13, 2016. / AFP PHOTO / SAUL LOEBSAUL LOEB/AFP/Getty Images

US President Barack Obama looks at a homemade spacecraft that was attached to a weather balloon and launched 78,000 feet up into the atmosphere by 11-year-old Rebecca Yeung (C) and 9-year-old Kimberly Yeung (L) as he tours the 2016 White House Science Fair in the East Room at the White House in Washington, DC, April 13, 2016. / AFP PHOTO / SAUL LOEBSAUL LOEB/AFP/Getty Images