Brian Sumers

How fickle is Wall Street? Less than a year ago, investors weren't keen on United's stock. But a couple of quarters later, they're jumping back on the bandwagon. But not all that much has changed.

So much can happen between now and 2021. David Neeleman's new airline may never get off the ground. But let's hope for the best. The U.S. airline industry could use its first new entrant since 2007 to stir up competition.

We're not sure Europe needs another airline with global ambitions. But more capacity almost always means cheaper fares, so passengers should enjoy watching these competitive dynamics play out. Perhaps Air Italy will become Italy's national carrier if Alitalia stops flying. Or maybe they'll both go bust.

Norwegian Air reported earnings Thursday, and a lot of analysts expected it to feel like a funeral. But something funny happened. The airline reported a profit. Does this mean it's in good shape? Probably not, but at least it's better than a loss.

U.S. airline consumers hate to admit it — they love bashing airlines, after all — but the competitive environment is strong right now, and considering rising fuel prices, fares are decent. But if there's a new entrant into the marketplace, like David Neeleman's proposed new carrier, things could get even better for customers.

Glitches happen and airlines lose money. But American probably could have handled last month's PSA Airlines debacle better. If it had, maybe it would have lost less money from the debacle.

U.S. airlines can reach some Western European airports profitably with narrow-body aircraft. But even the best narrow-body aircraft have some range issues. If it wants to fly to Europe, JetBlue will need to decide whether it can do so with the A321LR, or whether it should wait for a longer-range aircraft.

JetBlue's president and its CEO say they're not worried about competing with JetBlue's founder, David Neeleman, who may be starting a new U.S. airline as soon as 2020. Behind the scenes, we bet it's not their favorite idea. But we do believe they're not surprised Neeleman wants back in. Even since Neeleman was pushed out of JetBlue, insiders expected he would return someday.

Lufthansa Group's Airlinecheckins.com may not be the most amazing innovation ever, but considering it only took about 30,000 euros to build, the return on investment has been impressive. The platform allows customers to check in for flights on more than 200 airlines. And as the facilitator, Lufthansa gets a lot of data about passenger preferences.

Ryanair hasn't had the best year. Its reputation took a hit recently when it was forced to cancel thousands of flights because of pilot scheduling issues. But the customers have come back. Why? Cheap fares. It's the secret sauce.