Following in the steps of XM Satellite Radio, rival Sirius plans to offer a competing “always-on” weather service for aircraft through an agreement with data provider WSI. Plans are in place to launch a Sirius line of WSI’s InFlight avionics, which the companies say will be compatible with the current list of approved InFlight multifunction displays.

The Sirius satellite service will include “drop in” replacement antennas for operators flying with WSI’s AV001 InFlight antennas, as well as new Sirius receivers that will be compatible with WSI gear sold today. Pricing and feature options will be announced in the next few months, with the first Sirius-compatible InFlight products anticipated to be certified by year-end.

XM’s in-flight weather service has proved popular with pilots since its introduction a little over a year ago. Weather data provided by XM partner WxWorx includes Nexrad radar, graphical wind speed and direction, lightning strikes, METARs, TAFs and other information. Like the planned Sirius service, the XM version can overlay weather graphics on map displays in the cockpit. XM weather service plans start at $49 a month.