This article has content from Arrow S03E23 and Flash S01E22. So if you haven't watched these episodes, please don't go any further. SPOILER ALERT.
Ok, now that the mandatory spoiler alert warning has been issued, let's get on with the theory.
Coast City and Ferris airfield references have been around in CW TV Universe for a long time, no surprises there. But what has changed now is two instances where it was hinted directly at the possibility of the existence of the first human green lantern and Ferris Air Test pilot: Hal "Highball" Jordan.
The first hint was a not so subtle one that took place during the Flash's 22nd episode of the season.
This was a not so subtle hint at Hal Jordan's disappearance from Earth when he was taken to Oa to be presented in front of the guardians as the replacement Green Lantern of Sector 2814. Most of us would have picked up on that.
However, the second hint was actually a series of blink and you'll miss it tidbits. After Tatsu and Maseo's son Akio dies due to the infection from the bio weapon that was released in Hong Kong, the trio split up. Maseo goes to Nanda Parbat (Presumably) and Tatsu goes to her hometown in Japan. Oliver, however, doesn't return to Lian Yu or any other place that we might have guessed. He returns to Coast City, the City of Hal Jordan.
Ok, so, that might just have been a layoff, or a way for Oliver to get into the country without attracting unwanted attention. After all, travelling to coast city doesn't mean he would have met Hal Jordan.
However, the second hint was much more subtle and is more of an intuition than an easter egg.
Oliver crash lands a plane that has lost hydraulics and two engines with his newly married wife, Nyssa Al Ghul as his co pilot. Quite a honeymoon, you guys.
The thing is, when did Oliver learn to crash land a plan without hurting both the pilots? In fact, where did he learn to pilot a plane in the first place? Here's my theory. Oliver goes to Coast City, somehow meets Hal Jordan, they become buddies and Hal teaches Oliver to pilot a plane. Oliver comes to Starling City and becomes the Arrow, Hal becomes the Green Lantern and flies off to Oa.
As any comics fan would know, Green Arrow and Green Lantern are best buds and even had their own comic book for a while.
But as we have heard repeatedly, the CW TV universe and the Cinematic Universe are related. However, CW has been informed by WB that they can introduce any DC Character apart from DC's Holy Trinity: Superman, Batman and Wonderwoman.
Does this mean technically, we COULD see Green Lantern or at least Hal Jordan anytime in the next season?