Files question?!?!?

what can i use to open the various files of the microsoft p-55a default plane? i wanted to modify the weapons and manuevering effectiveness.
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https://forums.simviation.com/phpBB3/viewtopic.php?f=6&t=21632
<Loadout Name="(6)HVAR Rockets+(2)250lb Bombs">
<Hardpoint ID="1" PylonType="pylon_P55_0" PayloadType="A_250lb" Quantity="1"/>
<Hardpoint ID="2" PylonType="pylon_P55_0" PayloadType="A_250lb" Quantity="1"/>
<Hardpoint ID="3" PylonType="pylon_P55_1" PayloadType="A_HVAR" Quantity="7"/>
<Hardpoint ID="4" PylonType="pylon_P55_2" PayloadType="A_HVAR" Quantity="7"/>
</Loadout>
<Loadout Name="(6)HVAR Rockets+(2)250lb Bombs">
<Hardpoint ID="1" PylonType="pylon_P55_0" PayloadType="A_500lb" Quantity="1"/>
<Hardpoint ID="2" PylonType="pylon_P55_0" PayloadType="A_500lb" Quantity="1"/>
<Hardpoint ID="3" PylonType="pylon_P55_1" PayloadType="A_HVAR" Quantity="7"/>
<Hardpoint ID="4" PylonType="pylon_P55_2" PayloadType="A_HVAR" Quantity="7"/>
</Loadout>
<Loadout Name="(6)HVAR Rockets+(2)500lb Bombs">