We already have fly mode in test game, press F9 then pressing G turns gravity off, and the [ and ] keys are up and down. It's not very good, a little clunky, but it works.
i7 7700,k NV1070 8GB, 16GB 3200mhz memory, 1x 2TB Hybrid, Win10.
i5 4760k, NV960 2GB, 16GB 2333mhz memory, 1x 2TB Hybrid, Win10.
i5, NV1050 4GB, 8GB memory, 1x 1TB HDD, Win10.
i3, Intel 4000 series graphics, 6GB memory, 1x 500gb HDD, Win8.1.