On Tuesday Feb 09, 2016, Google announced that Flash ads will no longer be accepted by them.
From 30th June 2016, you will not be able to upload ads built in Flash format to Google Adwords and DoubleClick Digital Marketing
From January 2nd 2017, Google will stop displaying all the ads in Flash format through Google Display Network or through DoubleClick.
“Video ads built in Flash will not be impacted at this time”
In Feb 25, 2015, Google started to convert all the Flash based ads to HTML5, in order to make them run on mobile devices that do not support Flash. Before this update, google used to show a static image, if a device does not support Flash. After this update, when advertisers upload their flash based ads, they will converted to HTML5 automatically.
In September 2015, Google started to pausing Flash ads in Google chrome. This decision was taken by Google to improve the page load time and improving the battery consumption of mobile device.
Flash developer company, Adobe, has made it clear that they are adapting HTML5 and leaving Flash. Adobe has renamed Flash Professional as Animate CC in December.
Google said the move will “enhance the browsing experience for more people on more devices.” Advertisers are encouraged to migrate their ad formats to HTML5 ahead of the deadlines.
You can use this guide by Google to update your Flash ads to HTML5 ads.