What happened

Wednesday turned out to be a great day to own airline shares, with major carriers like Delta Air Lines (DAL -0.46%) soaring to close the day with double-digit percentage gains, or nearly so. By the end of trading, Delta shares were up 9.5%.

As the day wore on, even airlines such as Alaska Air Group (ALK -0.39%) and Hawaiian Holdings (HA -0.71%), which initially looked like they were going to sit out the rally, managed to climb on board and find a seat. By the closing bell, Alaska Air was up 9.2%, and Hawaiian scored a 10.9% gain.

Airplane maker Boeing (BA 0.15%) put in a strong showing as well. Up more than 5% at one point, Boeing shares closed the day with a 4.4% increase.

Airplane flying high against a background of clouds and sunbeam

Image source: Getty Images.

So what

Probably the prime driver behind today's gains for airline stocks was biotech Moderna's (MRNA -0.74%) announcement about its new mRNA-1273 coronavirus vaccine: The latest analysis of phase 1 clinical trials conducted through March shows that 100% of evaluated participants, over a range of dosages, ended up producing antibodies against the coronavirus.

Moderna's announcement is being taken as an early sign that it might soon be safe for folks to travel again, specifically by air. Such a revival of air travel would also revive demand for new airplanes from Boeing. 

Now what

Even before Moderna's vaccine is proved safe and effective (phase 2 trials are ongoing, with phase 3 trials set to begin in two weeks), the airline industry is working hard to get travelers back on airplanes. Today, The Wall Street Journal reported on "a major push to build confidence among travelers," through which airlines are arguing that airplanes are actually safer to be in than buildings, by virtue of airplanes' "brisk ventilation," "significant filtering," and "constant infusion of fresh air" from outside.  

So far, people don't seem to be buying these arguments. In Delta's earnings report on Tuesday, CEO Ed Bastian observed that passengers aren't lining up for new flights as fast as his airline had hoped, and that Delta will be slowing the reintroduction of flights to match the less-than-hoped-for customer demand.

Delta's also now projecting that September air traffic will be only about 25% of what it was a year ago, and that it could take "more than two years before we see a sustainable recovery" in air travel in general, while business travel (the most lucrative kind for airlines) may never again be what it once was.

That's a disturbing forecast. Lucky for owners of airline stocks, more people were listening to Moderna today.