What happens when (and if) the Boeing 737 Max returns to the air?

This September, the Boeing 737 Max — the airliner involved in two fatal crashes within five months that killed 346 people — will take to the skies for American Airlines once again after nearly six months of international grounding.

Reintroducing the 737 Max to American Airlines’ service will add 754 flights per week on 31 routes, overwhelmingly centered on Miami, according to the travel industry outlet the Points Guy. That means almost 131,000 new seats will soon be available to travelers.

If you’re flying in or out of Miami on American Airlines this fall, chances are it may be on a 737 Max. That is, if US politics don’t prolong the grounding further.

As reported by CNBC, American Airlines CEO Doug Parker told employees last week that whether the Federal Aviation Administration certifies the software fix required for the 737 Max’s reentry by the time the aircraft reappears on American Airlines’ schedule — September 4 — remains uncertain. “I think as much as anything now it may be politics as much as the true certification ... safety issue,” Parker said at his company’s recent town hall meeting, reports CNBC. “I don’t think the FAA wants to be alone in doing this.” Parker added that the 737 Max’s return may be pushed to October.

The international grounding has left many travelers in the lurch. Earlier this month, American Airlines announced that flight cancellations required by the grounding would eliminate 115 flights from its schedule per day through September 3. Max flights aren’t the only ones affected — according to the airline’s press site, “A flight that was not scheduled as a MAX flight might be canceled to enable our team to cover a MAX route with a different aircraft.” Southwest Airlines and United Airlines followed similar measures, with Southwest’s cancellations affecting 100 flights per day and United’s cancellations estimated at 2,400 flights in June and July alone.

Needless to say, more canceled flights are on the horizon if the grounding continues past Labor Day. A 737 Max flight might be available for booking online now, but that doesn’t mean that it’s, well, cleared for takeoff. Put another way: FAA certification isn’t required by airlines to sell seats on a 737 Max.

The most recent update released by the FAA on its ongoing investigation into the 737 Max tragedies details that “improperly manufactured” parts reported by Boeing are the current hurdle. FAA approval on so-called “software enhancements” of the MCAS system is what’s needed before the agency will lift the grounding; though as The Verge reported, significant human error at both Boeing and the FAA — rushed production, administrative incompetence, insufficient pilot training — remains largely to blame.

And it’s not just the FAA that stands in American Airlines and Boeing’s way. The Australian Broadcasting Corporation reports that more than 400 737 Max pilots are suing Boeing in a class-action lawsuit, citing an “unprecedented cover-up” of “known design flaws” and loss of wages following the airliner’s grounding worldwide. Boeing is reportedly on the verge of settling with the families of the crashes’ victims, according to Business Insider.

A lot needs to happen before the 737 Max comes back, even if your airline booking site tells you otherwise.

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