Depends who you are flying with.
The rules for US immigration are you can enter as long as your passport is valid under the visa waiver program.
Virgin same rules.
Other airlines could be different
This is taken from US customs and Immigration website, UK is signed up so we do not need 6 months validity.
As a general rule, passports must be valid for six months beyond the date the traveler will exit the U.S., however, the U.S. has signed agreements with a number of countries to waive this requirement. When such an agreement is in place, the passport must be valid for the entire period of the visitor's intended stay, but the additional six month validity period is not required