can`t install it on Apple MacBook Pro and Apple Air, Why

You don't explain what the error message is... also are you trying from Software Update or from a direct download?

Regards,

Shawn

If installing on 10.7.2, 10.7.1, or 10.7.0, you need to use the Combo update. If installing on 10.7.3, you can use the Delta update form Apple's website or Software Update application on the same Mac. You can't use the Delta update from Software Update application on another Mac on your Mac unless they are identical model and vintage. If installing on 10.6.8 or earlier, you must pay for 10.7 Mac App Store, or use a 10.7 installer USB stick first before applying it to your machine. Note: 10.7 does not support Rosetta. For other 10.7 pitfalls read this tip:

https://discussions.apple.com/docs/DOC-2465

Make sure all your software and hardware is ready for 10.7.4 before installing, and backup your data at least twice before installing, and disconnect the backup from your machine before installing.

A checksum error can happen with an unreliable internet connection, or one through a router that is malfunctioning, or has a proxy firewall improperly setup.

Also Apple servers are probably pretty busy serving folks Lion 10.7.4 & Safari 5.1.7 at the moment. It may be best to delay a few hours if you can.

Regards,

Shawn