What's up with airlines grounding more planes?

The bottom line: Yes, you should be worried but probably not for the reasons you think.
Over the past couple weeks, everybody's been reading about hundreds of flights being grounded because of maintenance problems. It started a couple of weeks ago when Southwest got hit with a record $10.2 million fine after admitting it missed required structural inspections on about 50 planes. And some days later the airline grounded dozens more because it wasn't sure that other necessary check-ups had been properly done.
In the past couple days, American and Delta have canceled hundreds of flights as they grounded scores of planes to inspect wiring. At Logan, this has ended up affecting more than a dozen flights.
No one wants to end up like Southwest.
But right now, with all these planes getting grounded for safety checks, you're getting kind of skittish about flying, yes. The airline wise guys say you're missing the point. In a story in the L.A. Times, they lay it out thusly: Yes, there is a safety issue, but it's not huge. Planes will not be raining down. What you are seeing is the result of an aging US fleet needing more maintenance at a time when carriers have less money to replace them and are trimming schedules to cut costs. As more planes need more work and with fewer options to reschedule we are going to start seeing more of these kinds of disruptions.
So air travel isn't necessarily less safe, but it could become a little less predictable.