The FAA proposes to adopt a new airworthiness directive AD for certain MHI RJ Aviation ULC Model CL-600-2B19 Regional Jet Series 100 and 440 CL-600-2C10 Regional Jet Series 700 701 and 702 CL-600-2C11 Regional Jet Series 550 CL-600-2D15 Regional Jet Series 705 CL-600-2D24 Regional Jet Series 900 and CL-600-2E25 Regional Jet Series 1000 airplanes. AD 2023-10-02 was prompted by the determination that radio altimeters cannot be relied on to perform their intended function if they experience interference from wireless broadband operations in the 3.7-3.98 GHz frequency band 5G C-Band. This AD was prompted by the determination that this interference can also result in certain failure messages being inhibited longer than intended. This proposed AD would require installing a new radio frequency RF bandpass filter on the coaxial line between the radio altimeter and the receive antenna in the aft equipment compartment. The FAA is proposing this AD to address the unsafe condition on these products.