Aviation Ground Marking to CASA Part 139 MOS: What Aerodrome Operators Need to Know

The call came from an aerodrome manager at a regional airport in country Victoria.

Their apron area needed a full remark — hold lines, aircraft parking positions, service vehicle lanes, safety zones. The aerodrome was due for a CASA safety audit in six weeks. The current markings had faded to the point where some were no longer distinguishable in certain light conditions.

'We've had two local contractors quote it,' he said. 'Neither of them mentioned CASA Part 139. One of them quoted it like a carpark.'

Aviation ground marking is not a carpark job. The standards are specific, the stakes are higher, and the approval requirements are real. A non-compliant apron marking at a certified aerodrome is a safety issue that CASA takes seriously.

We completed the job in two nights. The CASA audit passed without findings on surface marking.

Here's what aviation ground marking actually involves.

What Is CASA Part 139 MOS?

CASA Part 139 Manual of Standards (MOS) is the Civil Aviation Safety Authority's technical standard for aerodromes. Part 139 MOS Chapter 9 specifically covers aerodrome markings — the lines, symbols, and surface designations on aircraft movement areas.

The current version is the Part 139 (Aerodromes) Manual of Standards 2019. It applies to all certified aerodromes in Australia — not just major airports, but regional aerodromes, helicopter landing areas, and any aerodrome that holds a CASA aerodrome certificate. If your aerodrome is certified, your surface marking must comply.

The standard references the ICAO Aerodrome Design Manual (Doc 9157) for technical specifications and aligns Australian requirements with international standards. That means the marking scheme at a regional aerodrome in Victoria needs to follow the same logical framework as marking at major international airports.

The Key Marking Types and What They Mean

Runway Designation Markings

The runway number (derived from magnetic heading) painted at the runway threshold in white, at the specified dimensions in Part 139 MOS. The number and associated threshold markings need to be visible and legible from the air during approach — which means not just correct paint, but correct retroreflectivity and contrast against the runway surface.

Runway Threshold and Aiming Point Markings

White stripe markings at the runway threshold and aiming point at specified dimensions and spacing. The number of stripes and their spacing varies by runway width class under Part 139 MOS. This is not something to estimate — the dimensions are in the standard and they need to be followed precisely.

Taxiway Centreline Markings

Yellow continuous line along the taxiway centreline, 150mm wide, from the runway holding position to the apron. At intersections, curved guidance lines show the standard taxi path through the intersection. At holding positions, runway holding position markings (the double solid and double dashed yellow lines) indicate the point behind which aircraft must hold awaiting ATC clearance.

The runway holding position marking is one of the most safety-critical markings on any aerodrome. An aircraft crossing it without clearance is a runway incursion — a serious safety event. These markings need to be clearly visible in all conditions, including wet weather and low light.

Apron Markings

Aircraft parking position markings (lead-in lines, parking T's or boxes, alignment markings), service road markings, equipment parking zones, and safety clearance zones around aircraft stands. Each has specific dimensions and colour requirements in Part 139 MOS.

Apron markings also need to account for the equipment that operates on them. Ground power units, baggage loaders, fuel bowsers — all of these have operational clearance requirements that the marking layout needs to support.

Surface Condition Markings

Areas of the movement surface that are closed or have limited bearing strength may need to be marked. Yellow or red X markings for closed surfaces. Pavement condition indicators in areas with surface degradation.

Why Retroreflectivity Matters More in Aviation

In a carpark, retroreflectivity is about visibility at night for drivers at low speed. In aviation, it's about visibility during approach and landing in all conditions — including rain, low sun angles, and reduced visibility approaches.

Part 139 MOS references minimum retroreflectivity values for runway and taxiway markings measured in accordance with the MOS. Glass beads for retroreflective markings are specified to AS/NZS 2009. These aren't guidelines — they're minimum standards, and CASA inspectors check them.

We use retroreflective paint formulations with glass bead embedment on all aviation marking applications. Standard carpark paint, even premium paint, doesn't meet aviation retroreflectivity requirements. The glass bead specification and embedment depth for aviation applications is different from carpark applications.

The Colour Specifications

Aviation marking has a specific colour convention that differs from standard road and carpark marking:

• White: runway markings — thresholds, designations, aiming points, touchdown zones. White is used exclusively for markings directly associated with runway operations.
• Yellow: taxiway markings — centrelines, holding positions, guidance lines, apron taxi routes. Yellow is the universal colour for taxiway guidance.
• Red: mandatory instruction markings — runway holding positions (on the taxiway side), runway-to-runway holding positions, critical area boundaries. Red on white.
• Black: used as a background colour behind certain mandatory markings to increase contrast. Not used as a primary marking colour.

Using the wrong colour in an aviation context isn't just an aesthetic issue. A yellow marking where a white marking is required changes the meaning entirely and could cause pilot confusion.

Who Can Do Aviation Ground Marking?

Part 139 MOS doesn't prescribe specific contractor qualifications for surface marking — but it does hold the aerodrome operator responsible for compliance. In practice, that means the operator needs to use a contractor who understands the standard and can document compliance.

We've completed aviation marking at regional aerodromes in Victoria, New South Wales, and Queensland. On every job we provide:

• Pre-job marking layout drawings showing compliance with Part 139 MOS specifications
• Material certifications demonstrating retroreflectivity performance
• Post-job as-built drawings showing actual dimensions and positions
• Completion report referencing the specific Part 139 MOS sections met

That documentation package is what the aerodrome operator needs to demonstrate compliance to CASA. We've had aerodrome operators use our documentation directly in their CASA audit responses.

The Regional Aerodrome Job: How It Actually Went

Back to the country Victoria aerodrome. Two-night job. Night one was the taxiway centrelines, runway holding positions, and apron lead-in lines. Night two was the apron parking position markings, service road markings, and the runway threshold remarking.

We worked under aerodrome safety conditions — the aerodrome was NOTAMed closed for the marking nights, full traffic management plan filed, all crew inducted into aerodrome safety procedures. The job ran from last light to 4am each night.

Total surface marked: approximately 1,200 linear metres of taxiway centreline, 6 runway holding positions, 12 aircraft stand markings. Retroreflective paint throughout. As-built documentation provided within 48 hours of completion.

CASA audit six weeks later. No findings on surface marking. Aerodrome manager's feedback: 'First time we've gone through an audit without at least one comment on marking.' Sorted.

Frequently Asked Questions

Does Part 139 MOS apply to private aerodromes and helipads?

Part 139 applies to certified aerodromes. Not all private aerodromes are certified — if you're operating under a private aircraft operations approval rather than an aerodrome certificate, the strict Part 139 compliance requirement may not apply. However, best practice is to follow the standard for any surface used by aircraft. If you're unsure of your aerodrome's certification status, check with CASA or your aviation lawyer.

How often do aerodrome surface markings need to be renewed?

There's no fixed renewal period in Part 139 MOS — the requirement is that markings remain compliant (visible and meeting retroreflectivity standards) at all times. In practice, high-traffic aerodrome aprons may need remarking every 3-5 years. Runway markings at lower-traffic regional aerodromes may last longer. CASA inspectors assess condition during regular audits and will flag markings that no longer meet the standard.

Can you quote aviation marking outside Victoria?

Yes. We work nationally. Regional aerodromes across NSW, QLD, WA, and SA are all accessible. For regional aerodrome jobs, we factor travel and accommodation into the quote. Call Niel on 0417 460 236 to discuss your location and requirements.

What's the difference between apron marking and airside road marking?

Airside roads — the service roads used by ground vehicles on the airside of the aerodrome — follow a hybrid of aviation (CASA) and road (AS 1742) marking requirements. Vehicle lanes, give way lines, and pedestrian crossings on airside roads follow road marking standards. Aircraft parking and taxiway markings follow Part 139 MOS. We're familiar with both and will specify correctly for each zone.

What colours are used for aerodrome ground markings?

Aerodrome ground markings use white for runway markings such as thresholds and designations, yellow for taxiway centrelines, holding positions and apron guidance, and red for mandatory instruction markings. Black is only used as a background for contrast. Using the wrong colour changes what the marking means to a pilot.

What documents should an aerodrome operator get after marking?

An aerodrome operator should get layout drawings before the job, material certificates showing retroreflectivity, as-built drawings with actual dimensions, and a completion report listing the Part 139 MOS sections met. Line Marking Australia provides this package on every aviation job, so the operator can show compliance to CASA.

Line Marking Australia. Since 2009. 5,000+ projects. VicRoads approved. $20M public liability. $10M professional indemnity. Fixed prices. Full documentation every job. Call Niel: 0417 460 236.