Airport operator BAA's response to the pre-Christmas snow was "initially ineffective" leading to "distress" to passengers, a report into the December 2010 travel chaos has said.
Confused and contradictory messages caused incorrect signals to go to airlines and passengers, said the BAA-commissioned report.
The potential impact of the weather forecast was not fully anticipated in the days before the worst of the snow on December 18, it said.
This led to "a low state of preparedness ahead of the snow and insufficient stock of critical supplies for an event of this scale".
Clearing the aircraft stands was slower than required and slower than rates achieved elsewhere.
The report recommends that Heathrow adopts an improved winter resilience target that the airport should never close as a result of circumstances under its control, except for immediate safety or other emergency threats.
Thousands of Christmas getaway passengers had to camp in the terminals at the west London airport as airlines cancelled hundreds of flights.
BAA said it accept the report and is developing a £50 million resilience investment plan which it will recommend to airlines and the Civil Aviation Authority next month.
Led by BAA non-executive director Professor David Begg, the inquiry team concluded: "There were failures in communication and co-ordination within BAA, and between BAA and airlines, which led to ineffective engagement between different parties, resulting in ineffective situational awareness and a delay in response and escalation.
"The executive crisis management team and the capacity constraints group proved effective in managing the crisis once invoked. Both groups should have been mobilised earlier."