Jessica Simpson and Eric Johnson Side-by-Side on Vegas Flight

Jessica Simpson and Eric Johnson have been separated for a while now, but there are signs of a reconciliation in the air.

Check out JS and EJ boarding a Southwest Airline’s flight from Burbank to Las Vegas. The first thing we thought … maybe it’s a vacay with their kids, but there were no kids in sight.

They sat next to each other on the flight — yeah, we wondered too why they weren’t flying private.

We know why they’re in Sin City … they catching Ashley Simpson’s show at the Venetian. It’s the first night of her residency.

That’s especially interesting … why Eric would be there with Jessica if it’s a Simpson family event, but there he was.

They announced their separation in January but they’ve been apart for much longer, we’re told.