You can connect your laptop using a special PowerXtender adapter, which you can purchase from Xtend Micro Products. They have power status monitoring LEDs, and are airline quality compliant for safety as an external power source.
All models come with both airline and automobile connectors.
Xtend has adapters to fit hundreds of today's most popular notebook computers. In-flight phones Airfones are available in all United aircraft. The phone screen provides detailed instructions for placing a call. Additional information may be found within the Hemispheres Magazine. Rates also apply to 800 and 888 numbers.