There's something about air travel that gives Stephen Kellogg pause. When the wheels lift off, so does his mind soaring off into self-reflection. Maybe it's the proximity to the heavens, or the turbulence that imparts a trepidation that every sip from his mini-Coke can might be his last. Whatever it is, there is something about planes that prompts Kellogg to ponder his life.

Such was the case on a flight to Florida. As the plane bumped and bounced amid pockets of turbulence, he came to the conclusion that he was not satisfied with his music to that point. Sure, it was successful, enticing listeners from across the country with their tunes, spending hundreds of days on the road for what felt more like a vacation than an actual job. But to this point, Kellogg felt that they hadn't left anything … lasting.

“On that plane ride I thought, we gotta make an album where we say everything we can think of that we want to leave our family and our friends,” Kellogg says. “We can't take time for granted and just sing about things that we might think are kinda cool or are just a lark. We gotta say what we want everybody to know since, you know, in case things had gone differently. I got a little scared because I hadn't recorded a record that was the message I wanted to leave my wife and my parents and my buddies and all that.”

That changed with Glassjaw Boxer, the third, and latest, LP by Stephen Kellogg & The Sixers (who go by the handles of Kit and Boots). While the album still embodies the whimsical feel found on the band's previous records, it is tempered by a more serious tone. As Kellogg puts it, “We traded nostalgia for brutal honesty.”

Boxer provides a more personal feel than previous albums, with Kellogg singing more directly about the people and events of his life. But despite that, or perhaps because of it, the work could be their most relatable yet.

On “Fourth of July,” Kellogg croons of memories from his earlier days, before breaking into a chorus of “And this, this is my life / on the Fourth of July / It isn't much, but at least it's mine.” Amid scenes of missed opportunities, frequent failures and romances gone awry, Kellogg sucks you in with sympathy, an effect that Kellogg did not entirely foresee when he began writing the album.

“It's sort of an indulgent thing to do, [writing so personally], and I always shied away from it because I thought no one else was going to relate,” Kellogg says.

“I think it's a lot easier,” he continues, speaking of writing honestly. “When you're writing with an aim in mind, or if you're writing something that you're not totally sure about, it's a little more 'is this cool, isn't this cool?' You kinda go testing things out.”

While the inspiration for the honest and personal lyrics may have largely come from a perspective-inducing plane ride, Kellogg also notes that it was a performance by John Prine in Telluride, Colo., that made him comfortable with an altered approach to his music.

“I was just sitting there at his concert and had tears streaming down my cheeks. It was as good as anything I'd ever seen and he's just up there just him and his guitar,” Kellogg recalls. “Just watched his show and I got a sense of peace. Like, it's okay, just because we're entertainers doesn't mean we have to be entertaining every second. So it was a subtlety that hasn't been in our music before. That's something that's come into our music over the past two years. It was the more intimate moments and the way he was able to draw from that was very different. We'd always been a kind of jump-around-the-stage act, but I feel like we've gotten stronger with a few more of the chances we've taken.”

Though more serious than with their previous albums, Kellogg and the Sixers have still retained their slightly silly nature. (“It wasn't like we were in the studio saying, 'C'mon man, play the drums right because we could all die tomorrow,'” Kellogg jests.) And when the band plays live at The State Theatre May 1, both the silly and the sentimental sides of the Sixers are sure to be on display.

• Stephen Kellogg & The Sixers appear in support of Hanson on May 1 at the State Theatre. Tickets are $33 in advance and $35 on the day of the show. For more information on the band, visit www.stephenkellogg.com.