Small spoiler for tonight's episode of The Flash.
We finally get a direct reference to Green Lantern in The Flash – not just Ferris Air.
Both Ferris Air and Coast City have been mentioned many times in both The Flash and Arrow, but tonight saw mention made of a missing pilot. No specific name was given, but obviously it's a nod to Hal Jordan.
Now we get a Hal Jordan reference in the second last episode of the season.
It's possible whatever is being planned for Green Lantern may not just be a "movie," but a new Green Lantern series, with the "movie" being a crossover similar to what The Flash and Arrow had.
We're guessing more will be heard next season on The Flash about the missing pilot, with a Green Lantern reveal toward the end of The Flash Season 2 (similar to what they are doing now with DC's Legends Of Tomorrow) leading to the GL TV series in 2017.
Some other clues about Green Lantern include Arrow executive producers teasing they have better technology for flight; the president of the CW stated plans are underway for more spinoffs (note: plural), and most recently, David Ramsey stated DC has other plans for Green Lantern when it was brought up that Diggle might actually be John Stewart.
In addition, Stephen Amell teased Green Lantern at last year's 2014 Canada Fan Expo in his hometown of Toronto:
"Now, boy we've referenced Ferris Air a lot. It would be really cool to have Green Lantern. Hopefully, that happens. I have no inside information, unless I do."