4K HD Wallpaper: Airplanes on Sky
Marvelous 4K photography taken by Richard Verdoorn and available from his courtesy free under CC0 license. Download if you like and use in your desktop backgrounds, homescreen phones, social media, web design projects, blog articles, apps...
Widescreen Desktop / Macbook (Retina): 2880x1800 (fits on: 2560x1600, 1920x1200, 1440x900)
High Definition HD 1080p: 1920x1080 (fits on: 1600x900, 1366x768, 1280x720)
Samsung Galaxy Tab & iPad: 2048x2048 (compatible with many tablets)
HTC, Samsung Galaxy & iPhone: 1080x1920 (compatible with many phones)