Google Inbox Flight Scraper
First, go here: https://inbox.google.com/u/0/trips
Keep scrolling to the bottom until no more trips load.
Then open the developer console and paste the code below. Leave it alone for a few minutes. Once it's done scraping your flights, click the link it prints to the end of the console. This will take you to gcmap.com, which will then ask you to disambiguate the city names (e.g. "Washington DC")