What is the correct phraseology for stating a magnetic heading of 90 degrees?

The correct phraseology for stating a magnetic heading of 90 degrees is "Heading Zero Niner Zero." This phraseology follows the standard aviation communication practices set forth by the Federal Aviation Administration (FAA) and other aviation authorities, ensuring clarity and precision in air traffic control communications.

When issuing headings, it is essential to include all three digits to avoid any confusion. Therefore, “Zero Niner Zero” explicitly indicates the full 90-degree heading. This ensures that both pilots and air traffic controllers are on the same page regarding the intended direction, as any ambiguity in communication can lead to dangerous situations in aviation.

Other options lack the complete and clear representation required; simply stating "Ninety" or "Nine Zero Zero" does not comply with the standard phraseology where the "zero" prefix must be used to denote the leading zero before the nine, which is crucial in this context. "Magnetic Heading Nine Zero" is also not used in standard phraseology, which prefers the more explicit and standardized formats.