South African travellers flying this summer could face unexpected baggage restrictions, reduced passenger numbers and flight delays as soaring temperatures affect aircraft performance at Johannesburg’s OR Tambo International Airport and other high-altitude airports.
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According to a report by The Citizen, South African Airways (SAA), Airlink and LIFT have confirmed that exceptionally hot weather can force airlines to reduce aircraft weight before take-off. This could mean removing cargo, separating luggage from passengers or, in some cases, limiting the number of people on board to ensure a safe departure.
Why does hot weather affect flights?
The issue comes down to air density. As temperatures rise, the air becomes thinner, reducing the amount of lift an aircraft’s wings can generate and the thrust produced by its engines. This can increase the distance needed for take-off and affect how well an aircraft climbs after leaving the runway.
The problem is particularly relevant at OR Tambo, which sits approximately 1 694 metres (5 558 feet) above sea level. Its elevation, combined with high summer temperatures, creates challenging take-off conditions for aircraft.
LIFT’s chief pilot of flight operations, Warren Penney, explained that temperatures above 30°C require particular attention, although there is no single temperature at which airlines automatically have to restrict passenger numbers.
Instead, each departure is assessed according to several factors, including temperature, air pressure, wind, runway conditions and the aircraft’s weight.
How much can aircraft weight be reduced?
SAA’s aircraft performance modelling highlights just how significantly extreme heat can affect take-off weight.
According to spokesperson Mphilo Dlamini, an Airbus A330’s maximum permitted take-off weight could decrease by as much as 20 tons when temperatures rise from 25°C to 40°C.
Other aircraft face similar restrictions. An Airbus A320, for example, could have a permitted take-off weight of approximately 77 tons at 25°C, dropping to 73.5 tons at 40°C.
For larger aircraft, the difference can be even greater. An Airbus A340’s permitted take-off weight could fall from 261 tons to 227 tons over the same temperature range.
Long-haul flights departing from Johannesburg are particularly vulnerable because they require more fuel, leaving less weight available for passengers, luggage and cargo.
Dlamini’s example of an A340 carrying 80 tons of fuel illustrates the challenge. Under cooler conditions, the aircraft could have approximately 44 tons available for its payload. At 40°C, that figure could drop to just 10.5 tons.
Will passengers have to travel without their luggage?
Not necessarily. Airlines have several ways of managing aircraft weight before resorting to passenger restrictions.
Airlink explained that cargo would generally be removed first, followed by adjustments to fuel loads where regulations allow. Baggage restrictions and removing passengers would only be considered if other measures were insufficient.
However, certain cargo will always take priority. Critical items, including lifesaving medication and human organs intended for transplants, would not be offloaded.
Airlines may also adjust departure times to avoid the hottest part of the day. Early morning and evening flights can offer more favourable conditions, although rescheduling services can affect connecting passengers, subsequent flights and crew schedules.
What should travellers expect this summer?
While these restrictions are not guaranteed to affect every flight, passengers travelling during particularly hot periods should be aware that aircraft weight limitations can influence departure plans.
Travellers with connecting flights may also want to allow sufficient time between services, as delays to one flight can affect the rest of an aircraft’s schedule.
Importantly, these measures are safety precautions rather than signs that an aircraft is unsafe to fly. Airlines calculate the permitted take-off weight for each departure to ensure that aircraft can take off and climb within their operating limits.
For now, passengers flying from Johannesburg and other elevated airports should keep an eye on airline communications during the summer months, particularly on days when temperatures are expected to climb.
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