# Applicability of 90-Day Rule for Intermixed Airplane Engines and/ or Nacelles
> **Rule** · Statement of policy. · Published 1999-11-23 · 64 FR 65655
## Document
- **Document number:** 99-30502
- **Category:** other
- **Type:** Rule
- **Action:** Statement of policy.
- **Citation:** 64 FR 65655
- **Publication date:** 1999-11-23
## Abstract

This document clarifies the continued applicability of the 90- day limit for certain changes in airplane type designs after the final compliance date requiring an all Stage 3 fleet in the contiguous United States. The Federal Aviation Administration (FAA) has received numerous inquiries regarding the use of the 90-day limit after December 31, 1999. This document provides guidance to operators that need to use that provision of the airplane type certification regulations, including the limits of its use.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/1999/11/23/99-30502/applicability-of-90-day-rule-for-intermixed-airplane-engines-and-or-nacelles)
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