Canberra Airport plans to use its 24-hour curfew-free status to become Sydney's freight airport.

Overnight freight out of Canberra Airport will relieve Sydney residents of noise and free up land, allowing Sydney to expand commercial passenger services, according to a draft master plan.

Setting out Canberra Airport's development for the next 20 years, the 2014 draft master plan, on public exhibition until June, says most Canberrans will be spared noise from overnight freight aircraft. The exceptions are some homes at Jerrabomberra and the new Tralee suburb, which are outside noise abatement areas.

Greens MLA Shane Rattenbury opposes a freight hub.

He said the noise would disturb residents at Kingston Foreshore, the new Eastlake subdivision, in Gungahlin and north Canberra.

''I think Canberrans don't want to inherit Sydney's night-time noise and the only fair way to deal with the airport is to put in place a clear regulatory environment now, so they don't spend a lot of time and money building up a freight hub that later on will become a problem,'' he said.

A rail freight hub would create economic growth and be more environmentally suitable. ''This [air freight strategy] is premised on Canberra becoming a dumping ground for Sydney's night-time aircraft noise and if there is a second Sydney airport without a curfew, which will be part of the plan, that would undercut the Canberra Airport's strategy,'' Mr Rattenbury said.

The master plan acknowledges public concern about noise, but says the impact is lessened because most Canberra and Queanbeyan homes - 165,000 homes - are outside designated noise areas.

Only 750 homes are within the 20 ANEF (noise contour map). Sydney is Australia's largest origin and destination for express overnight freight, but has a curfew that restricts overnight operations.

Canberra Airport is in talks with overnight air freight operators, including one carrying trans-Tasman overnight freight who is interested in using Canberra rather than Sydney.

The airport expects its freight hub to begin operations in five to seven years, with two to three jet freighter aircraft a night, and growing to five aircraft, according to the master plan.

The frequency and size of of aircraft are forecast to increase indefinitely into the future, arriving and leaving late at night and in the early hours of the morning.

Within 20 years, should the business be established, about 1000 people would be employed in the freight industry at and around the airport, and between 5000 and 7000 people in associated businesses.

In the first stages, the airport expects one to three B-double trucks a week leaving the airport for Sydney.

Growth of the overnight air freight hub over the next 20 years may bring trans-Tasman flights to Christchurch, and more direct services for Tasmania, Alice Springs, Darwin and north Queensland, adding three nightly aircraft operations, most likely smaller jet or turboprop aircraft.

More freight infrastructure would be built in coming decades, with trucks to match.

It is expected international airfreight services to Canberra will grow gradually, commencing with one airline operating two to three weekly B747-800F (or equivalent) services to and from Canberra in the next five to seven years.