A practical test, more commonly known as a checkride, is the Federal Aviation Administration examination which one must undergo in the United States to receive an aircraft pilot's certification, or an endorsement for additional flight privileges. The name refers to the portion of the examination in which the candidate being examined flies in an aircraft with the Designated Pilot Examiner or other authorized examiner to demonstrate competency in the skills that are required for the certification. Although "checkride" is the most commonly used term, it is considered informal and is technically known as a Practical Test by the FAA and in all its literature, and the specific objectives which the candidate must meet are called the Airman Certification Standards, or ACS. In addition to successfully completing a checkride, one must also complete an oral examination, and meet certain basic aeronautical experience requirements as well as pass a separate multiple-choice computer-administered test that is quite consistently called the "written test." During a checkride, an examiner takes on a role more like that of a passenger rather than an instructor. That is, it's the examiner's job to observe that the candidate demonstrates good decision-making skills, rather than to teach or to act as a crewmember, although an examiner is likely to offer advice during the ride if so inclined. The examiner usually does not touch any of the aircraft controls unless necessary to maintain the safety of the flight — in which case the candidate usually fails the examination instantly, except for the part when the examiner acts as a safety pilot during operations with a view limiting device. While the Airman Certification Standards outline very specific tolerances that a prospect must adhere to, the examiner has a certain amount of subjective control over whether the student passes or fails. When a candidate fails a checkride, the examiner has the discretion to either end the checkride immediately, or allow the student to complete the remaining objectives of the checkride, and defer the failed task to a retake. The checkride may not continue without the consent of the applicant. During the retake, the examiner is only required to test the previously failed or uncompleted items, but is at liberty to retest any items previously passed, as well as fail the candidate again based on them. If the checkride has to be stopped due to any reason besides student pilot failure, e.g. weather setting in, the examiner will issue a letter of discontinuance, which will state which maneuvers have been completed, so that the re-take checkride can be limited only to the maneuvers that haven't been completed yet.