A UK Border Force spokesman said: "We flexibly deploy staff to meet demand, meaning that the vast majority of passengers pass through immigration controls quickly.
We will not compromise border security but work closely with airport operators to keep delays to a minimum."
More top news
The PM faces a countdown to settle a deal before her minority government tries to get its Queen's Speech plans approved by the Commons.
More details will come today on proposals to offer EU residents the right to a new "settled status" in Britain after it leaves the bloc.
Scotland and Northern Ireland could see rain later but for the rest of the UK it should be a fine day.