"Yep."

"And what should have taken us to LA."

"Yep."

They should in fact have the California coast in their sights, by now, with visibility this good, though LA would still be more than a hundred miles away. Navigation errors can lead you surprisingly far astray, but - Baja California maybe, or San Francisco maybe, there's no fathomable -

"- I'm out of explanations."

"Doesn't really matter, right. We've gotta get her down. Next radio callout, tell them our intentions are to navigate visually and descend to 200 and see if we can catch any landmarks, and that we are actively looking for a safe place to land."

"This is emergency aircraft Southwest Airlines 8684, position unknown, flight level 360, descending to 200, visual navigation, looking for landmarks" he transmits on the emergency frequency, though at this point with a sense that they're definitely shouting into the void. "Uh, 14,000 pounds of fuel and a hundred seventy five souls on board. We're looking for a safe place to land."

He gives hypothetical air traffic control which can hear their transmissions fine some time to move other planes out of their way and then begins the descent, though he too does not really believe that air traffic control can hear their transmissions fine. Even at 200 they'll be well above the mountains they've just passed. 

"We could consider reengaging the autopilot, if it's not the problem."

"I guess it'd be good to have both sets of eyes peeled." He re-engages the autopilot to manage the vertical descent, then looks back up out the windshield.  "Oh hey, look ahead, that's a big lake. There's our worst-case scenario, then."

"- that's got to be enough of a landmark to figure out where we are. That's - the size of Lake Michigan, or something -"

"And I think that might be civilization next to it, though at this height I'm not sure." It's certainly not a city, but a small town, maybe, or an abandoned Air Force base - there are some things that look like regular lines -

He's consulting a map. "It continues to not make any sense for us to be in central America but that could in principle be Cocibolca, near Managua, though we shouldn't have flown over any mountains to get there. It could be, uh, Maracaibo in Venezuela? If so, the sea should be right north of it -"

The lake is misty enough he can't see the far banks. "Could be."

"Those are, to be clear, both much smaller than Lake Michigan, but maybe we're misestimating the size because we're trying to visually navigate under weird conditions -"

"- maybe, but I don't think so. That's a big lake, there. I've flown over Salt Lake City at 200 and that's bigger than Salt Lake."

" - it's called Great Salt Lake."

"Well, I may not know what it's called, but I know what it looks like at 200. What bigger lakes are there."

"Central and South America do not actually appear to have any lakes the size of Lake Michigan. ...and also, we would've run out of gas, and the heading is wrong."

"Right, so, the lake doesn't suggest any new frequencies to try and we can't look it up to find our minimums," he says curtly because continuing this line of inquiry seems like it'll at this point be distracting.

"I'm, uh, really kind of feeling like we're not in Kansas anymore, so to speak."

"I want to try broadcasting more frequently, on more channels. In case they have radio but aren't listening to the standard emergency frequencies for any reason," such as "time travel" or "we are on an alien planet" or "we are overflying the lost continent of Atlantis which just resurfaced" or whatever else. "I'm going to stay at 200 for a while, follow the coast of that lake when we reach it and see if there's a city anywhere."

Sure, he'll cycle through frequencies repeating himself. They are emergency aircraft Southwest Airlines 8684. They do not know their position. They believe they're at flight level 200. They believe they're at heading 062. They have 13,000 pounds of fuel remaining. They are approaching a very big lake in about a hundred miles and they cannot find the very big lake on their maps.

They do not get any responses by the time they've reached the lake.

"You see any roads or runways?"

"Nope." Seen up a little closer, those are definitely buildings, but not runways. And none of the distinctive squares of intensively cultivated farmland, either. You could probably land a plane like this in a cornfield, intensively graded and levelled and all the rocks and ridges and so on removed. You can't just land it in an ordinary field; it's too big and heavy, lands too fast and rolls for too long, and it'll hit rocks and trees and come apart. 

"Gonna follow the coast of Lake Mystery here, see if we find something bigger than a village as we go. Why don't you take a look at the checklists for a ditching in Lake Mystery."