Another entry in the "I hate cats, but love..." family.
If I haven't mentioned it earlier, I love flying. I've spent hundreds of hours in private aviation aircraft (both fixed wing and rotor). The fighter pilot creed goes: Speed is Life. For a manticore, that isn't the case. They are poor/clumsy/whatever edition description of flyers. Effectively this means that they move in straight lines, making it easier to deal with 3 dimensions.
What makes up for their poor flight is that they have an omni-directional long range attack - tail spikes. 24 of them to be specific, all at a decently high attack bonus and damage output. So use them, use them all, if you haven't worn down the party enough for the manticore to swoop in and grab a snack, then have the manticore leave the area. If however, you do have a nice, tasty dinner laying on the ground, then what happens?
Well, depending on your edition, feats can allow a manticore to have hover, fly-by attack, grab, etc. Otherwise, just make it up. If that halfling thief is laying motionless on the ground, then there's no reason you cannot get creative with how the manticore takes it's lunch to go. (It might even spark some creativity in your players.)
But what happens when the manticore lands? Simple, it doesn't, unless everything is laying on the ground dying. If the party is to powerful for the manticore to attack directly or alone, they have great tracking ability. Have it follow the party for awhile, days even. Then when the party gets preoccupied with something else, like camping, climbing a mountain, crossing a river on a rope bridge, fighting a different creature - BANG, BANG, BANG, BANG and that nice juicy mage/sorcerer/summoner is a piece of manticore cheese, just waiting to be picked up at the next window.