A water table is always a fun activity that is age appropriate. We used to have one at a daycare I worked at and the children loved splashing around, playing with buckets and water toys...

Play silly games like red light green light.

Chalk as another PP mentioned.

Do arts and crafts activities outside. Finger painting is always a blast, especially outside.

Plan a scavenger hunt. Give him a piece of paper with the objects to be found. (A ball, a leaf, a stick...)

I'm sure I could come up with other ideas but those were the few that came to mind.

Chalk, kiddy pool, picnic outside.

Get a little garden box or sandbox for the backyard that he can dig in. Then he can play in the dirt, dig up buried treasure, hunt for worms/bugs, etc.

Does he have any kind of ride-on or push toys? Something like that would be appropriate at 2yo.

Even with the best yard and the best activities, 2 year olds are often easily distracted, so I wouldn't worry if he only plays for a few minutes before hunting for airplanes (if that makes him happy, keep it up!)

Hmm. I'm having trouble finding something that keeps him interested for more than a few minutes. It's a concrete yard, may be 30'x30'. (We're in NYC, so that is a relatively a big yard.) He has a few balls. I've tried various versions of catch. We've rolled the balls off his slide. He lost interest in the slide after about a week. He'll blow bubbles for a few minutes. I try to encourage "games," but he just looks for planes in the sky. I sing songs and try to get him to do the hand motions. He seems so bored out there. I feel as though I am just not giving him activities that interest him. He did have a little scooter, but for some reason the parents have put that away.

Any ideas? The parents are open to buying toys if need be.