Proof of citizenship is required. United States, Canada, United Kingdom, and CARICOM citizens may present a driver's license or other government photo ID; all others require passports.You can find a list of countries requiring visas here (https://www.immigration.m...). You can apply for a visa on the same website.
Several tour operators in Antigua offer day excursions to Montserrat, including observation of the Soufriere Hills volcano. Charter helicopters from Antigua offer another way to view the volcano.
Fly Montserrat offers multiple daily flights out of Antigua into the John A. Osborne Airport IATA: MNI. Prices as of Nov 2011 were approx USD200 round trip, including all taxes. Note that the planes are twin engine turbo props that hold a maximum of six people, with limited luggage space. The flight is approx 20 minutes total, with amazing views or Antigua, Montserrat, and other islands off in the distance.
The primary transportation harbour is Little Bay, near the de facto capital of Brades. As of November, 2011, regular ferry service from Antigua continues. (http://www.visitmontserra...) Service is not available every day, so checking the schedule in advance is advised.