Scattered digital lines across screen

There are a small number of softwre issues that can cause this kind of problem, but before digging any further, there are two hardware resets that might help.

The first is resetting PRAM (the non-volatile memory where system settings are stored). To reset this, shut the system down, and then press the power button to the right above the keyboard to power on the MacBook Air. Immediately press and hold the "Command-Option-P-R" keys until you hear the startup tone twice.

In some situations that may resolve an issue of this kind. If it doesn't help, the next is a System Management Controller (SMC) reset. Again, shut the MacBook Air down, make sure the power adapter is plugged in, and then; On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time. Then release all the keys and the power button at the same time. Then press the power button to turn on the computer.

test it to see if that has resolved the problem. If not, post back with any further details you can, such as whether this issue happens when running any particular software, or under any predictable and repeatable circumstances.