The monarch's planned meeting Wednesday with former Irish Republican Army commander Martin McGuinness follows her visit to Enniskillen, where a no-warning IRA bomb in 1987 killed 11 Protestant civilians as they commemorated dead from the two world wars.
The queen's aircraft landed Tuesday at the main Royal Air Force base in Northern Ireland after her aircraft was diverted to avoid foul weather at Enniskillen's airport.
She is expected to meet bombing survivors and attend services in the town's neighboring Protestant and Catholic cathedrals.
Worldwide revulsion at the Enniskillen slaughter spurred McGuinness and other IRA chiefs to begin exploring peace terms with Britain.