The keyboard and trackpad on a MacBook Air both connect to the logic board, but not to each other. If you experience an issue with your keyboard and trackpad at the same time, you most likely have a software-related issue. In some cases, if you know the circumstances surrounding the time that the keyboard and trackpad stopped working, you can figure out what went wrong.
Liquid Spills
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Spilling liquid on your computer can cause harm to the internal circuitry. The backlit keyboard attaches to the top part of the metal casing inside of the Mac. Because of this, if you quickly turn your MacBook Air over following a spill, you might prevent damage to the circuit board. Turn your computer off and let the computer air out for at least three days. After a spill, if you experience a problem with the keyboard or trackpad after turning your computer on, you need to power off your computer and take it to a professional to have the computer cleaned. Otherwise, you risk corrosion and damaging additional components.
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Software Update
Occasionally, outdated system software can prevent your MacBook from running properly. Apple releases fixes through Software Update to correct issues that prevent your hardware from functioning appropriately. Before attempting any invasive troubleshooting steps, check for and install the latest updates for your system. Click the Apple menu, select "Software Update..." and choose the "Update All" button to update any available software. After updating your software, restart your computer to see if the issue remains.
Windows Conflicts
During the installation of Windows 8, the Mid-2013, 13-inch MacBook Air may stop responding during the Personalize step. This affects the ability to use both the keyboard and the trackpad. The stall occurs as the result of some USB 3.0 drives. If this occurs with your installation, try using a USB 2.0 drive to install Windows or the Apple drivers. The installation using a slower USB 2.0 drive takes longer, but according to Apple Support, doing so can correct the issue.
Reset the SMC
Sometimes you need to reset the System Management Controller. The SMC controls many low-level functions on a Mac including non-responsiveness after opening and closing the display on your Mac. It can also affect the backlighting on the keyboard and other hardware-related issues.
Before resetting the SMC, put your computer to sleep and then wake your Mac. Restart your computer and then shut it down completely after it restarts. This can resolve the issue without an SMC reset. If the trackpad and keyboard still don't work, shut down the computer and plug in the power supply. Press the "Shift-Control-Option" keys on the left-hand side along with the power button simultaneously. Release all of the keys and then power on the computer. You may see the charge indicator light blink between orange and green.