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    Crossing the Gulf of Mexico

    One topic that continues to come up with new customers of ours is the requirement for crossing the Crossing the Gulf of Mexico (GOMEX). The airway structure of GOMEX was updated back in 2013 and the old "colored" airways (Amber, Blue, Green and Red) were replaced with new L-Lima and M-Mike airways. The Lima and Mike airways across the GOMEX are RNP-10 routes and authorization is required from the civil aviation authority of the country of registry via a Letter Of Authorization (LOA). So, if you plan to fly across the GOMEX and wish to fly an "N" registered aircraft on a Lima or Mike airway, you will need a LOA from the FAA. There is often a misconception as to the equipment capabilities of the aircraft versus having an LOA. Regardless of what the navigation equipment on board your aircraft can do, you must still have a specific LOA for flying on a RNP-10 airway to use these airways.

    However, all is not lost if you do not have an LOA. When the airways were redesigned, the FAA and Mexico's SENEAM left two colored airways A770 and A766 which can be used by those aircraft that do not have an LOA for RNP-4 or RNP-10 operations. In discussions with Houston Center on behalf of our non RNP-10 customers, they have indicated that you should plan and file for the colored airways and when in the air you can always request a Lima or Mike route if they are available. By planning for the A770 or A766 routes you can ensure that you have adequate fuel and range in the event that the Lima and Mike routes are unavailable to you. Plan for the worst, hope for the best.

    For those that are RNP-4 and RNP-10 approved, don't forget to put L1 and/or A1 in your PBN codes so that ATC can identify that you are authorized for those airways. For more information on GOMEX operations, visit the link below.

    Operational Policy/Procedures for the Gulf of Mexico 50 NM Lateral Separation Initiative (faa.gov)
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    If you are going to file for a Lima or Mike route you should insert "RMK/NONRNP10” in Item 18 of your flight plan. If ATC can accommodate you they will but preference will be given to conforming aircraft. This is why we recommend that you plan for one of the Amber routes to ensure that you have the range and then when airborne request the Lima or Mike route you would prefer to fly. This is also what Houston Center has recommended to us as well. However, for your return to the USA northbound, we have found that Merida Center is not quite so accommodating. When filing a flight plan south of the border you really do want to plan and file the Amber routes.

    Unfortunately, we see quite a few instances where we see PBN/A1 or PBN/L1 on proposed flight plans for aircraft that we doubt have an LOA. When we ask the question if they have an LOA, the answer is often "what's that?"

    Another common mistake US pilots make is that the Amber, Blue, Green, Red, Lima and Mike routes can only be flown both in the Lower and Upper Information Regions (LIR / UIR) in US controlled airspace. When you reach the Flight Information Region (FIR) boundary with Mexico, Cuba, etc. A, B, G, R, L, M routes can only be flown in the LIR and you must then fly the "Upper" airway, UA, UB, UG, UR, UL, UM to proceed in the UIR.

    For example: SBL L208 DUTNA UL208 CPE

    While the FAA probably won't say anything when you file and get a clearance, Merida Center will probably correct you when you get handed off to them. When filing a flight plan for the return northbound, the local ATC will definitely not accept a flight plan for FL430 on L208, they will require UL208. Similarly, UL208 ends at the FIR boundary (Mexico-USA) so you would be required to file CPE UL208 DUTNA L208 SBL

    Please remember, I am but the messenger, not my idea......

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