Narrative:

We were on an international flight. At FL340; 20mins into the flight; we advised ny center that we needed to deviate 20 miles to left of course due to thunderstorm activity. We were cleared for 25NM left of course. Before being handed off on an HF frequency we advised ny center that we had only VHF communications capability but do have a satellite phone on board. Ny center gave us a commercial radio company phone number and told us to report our next fix with them and then to contact ny center on a VHF frequency 45 miles south of marig intersection. We reported our next two fixes with the commercial radio company on the satellite phone. 10 minutes later we needed to climb to FL360 due to thunderstorm and lightning. We tried to reach the commercial radio company but there was too much static. We were able to communicate with another airline flight on guard; however; who passed on our request to ny center for a climb to FL360. They advised us that ny approved the request. After continuing for another 15 minutes at FL360 we needed to climb to FL380 to deviate from another set of thunderstorms. After deviating to FL380 we contacted the commercial radio company on the satellite phone and informed them of our deviation. They advised ny center and ny center advised them to have us expedite to FL370. We stayed on the phone with the commercial radio company to confirm our altitude at FL370 and reconfirm our next two fixes and our deviation of 25NM left of course. They then advised us to contact ny center on a new frequency; which we did. Ny center gave us a phone number to call them when we landed due to a pilot deviation. On the ground we called and explained to them the reason for the deviation; which was necessary for safety of flight. They advised me that we were in conflict with another airplane at FL380.

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Original NASA ASRS Text

Title: Cessna 510 in oceanic airspace climbed to FL380 without a clearance to avoid thunderstorms.

Narrative: We were on an international flight. At FL340; 20mins into the flight; we advised NY Center that we needed to deviate 20 miles to left of course due to thunderstorm activity. We were cleared for 25NM left of course. Before being handed off on an HF frequency we advised NY Center that we had only VHF communications capability but do have a satellite phone on board. NY Center gave us a commercial radio company phone number and told us to report our next fix with them and then to contact NY Center on a VHF frequency 45 miles south of MARIG intersection. We reported our next two fixes with the commercial radio company on the satellite phone. 10 minutes later we needed to climb to FL360 due to thunderstorm and lightning. We tried to reach the commercial radio company but there was too much static. We were able to communicate with another airline flight on guard; however; who passed on our request to NY Center for a climb to FL360. They advised us that NY approved the request. After continuing for another 15 minutes at FL360 we needed to climb to FL380 to deviate from another set of thunderstorms. After deviating to FL380 we contacted the commercial radio company on the satellite phone and informed them of our deviation. They advised NY Center and NY Center advised them to have us expedite to FL370. We stayed on the phone with the commercial radio company to confirm our altitude at FL370 and reconfirm our next two fixes and our deviation of 25NM left of course. They then advised us to contact NY Center on a new frequency; which we did. NY Center gave us a phone number to call them when we landed due to a pilot deviation. On the ground we called and explained to them the reason for the deviation; which was necessary for safety of flight. They advised me that we were in conflict with another airplane at FL380.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.