Per the Federal Register Notice linked here, the FAA random rate will remain the same for 2019—25% for drug and 10% for alcohol.
Also, although no Federal Register Notice has been published to date, the Federal Transit Administration announced in their October Regulatory Update publication that effective January 1, 2019, the minimum rate of random drug testing will increase from 25% to 50% of covered employees for employers subject to FTA’s drug and alcohol regulation. This change is due to an increase in the industry’s “positive rate” as reflected in random drug test data for calendar year 2017. The alcohol testing rate is unchanged for 2019 and will remain at 10 percent.