Three passenger aircraft "narrowly missed" a step ladder that fell off the back of an airport maintenance truck and was left on the runway as they landed, an investigation has found.
The probe said the 7ft (2m) item was not removed until after the third plane had touched down at Birmingham Airport.
Aviation authorities have ruled a bungee cord fastening to secure the ladder was not suitable.
The airport said it had since changed procedures.
Nobody was hurt by the object's presence in the middle of the runway and none of the planes were damaged, but a report by Air Accident Investigation Branch (AAIB) said: "With landing speeds in excess of 120 [knots], an aircraft hitting an object such as the ladder may have resulted in substantial damage.
"In this case, taking the position of the ladder on the runway into account, and the main and nose landing gear track width, all three aircraft narrowly missed the ladder."
The AAIB said the ladder was among the apparatus of two airport technicians who had been working on Runway 33's approach lights on 8 September 2020.
As they accelerated on the way to their next task, the ladder fell from their truck and "came to rest just to the right of the runway centreline", the report found.
Three aircraft later touched down with the item in their sight.
The crew of the second aircraft, a Boeing 737, was first to alert air traffic control, reporting that an unknown object appeared to be on the runway.
The crew of the first plane, also a Boeing 737, then reported it had seen something similar.
The third aircraft, a Boeing 757, was warned there could be something on the runway, but the crew decided to land and then reported seeing a step ladder.
The object was then found near the "touchdown zone".
The report said a bungee cord used to secure it to the truck came from the maintenance organisation's own supplies and while more suitable securing equipment was available, it was not readily to hand.
"At first sight the bungee may have seemed suitable to secure the ladder", the investigation found, but added the way it was attached to the truck was unsuitable, because it was stretched almost to its limit.
An airport spokesperson said the site had carried out a full investigation, with changes identified.
A statement read: "The vast majority of these plans have now been actioned, which include the revision of procedures, issuing of specific control measures and practical assessments. We have also focussed on training and harmonisation of working practices, involving and engaging with employees across the operation to empower and embed the changes.
"We are extremely grateful to the AAIB for their comprehensive report and we stress that Birmingham Airport is committed to providing a safe and secure environment for all who use the facility."