Google has announced that its Google Display Network and DoubleClick Digital Marketing (DCDM) platforms will begin phasing out the use of Flash ads starting June 30th. From the start of July through the end of the year, advertisers will no longer be able to upload Flash ads into AdWords or DCDM. And, starting January 2nd, 2017, any existing Flash ads will cease to function on any of Google's ad networks. This only applies to static ads, mind you. Flash-based video ads will not be affected.
Source: Google