Section 121.1 - First-Class Mail(a) A same day service standard is applied to USPS ConnectTM Local Mail pieces properly accepted at participating Destination Delivery Units before the day-zero Critical Entry Time (CET); a one day service standard is applied to USPS ConnectTM Local Mail pieces accepted via carrier pick-up or properly accepted at participating Destination Delivery Units after the day-zero CET.(b) A 1-day (overnight) service standard is applied to intra-Sectional Center Facility (SCF) domestic Presort First-Class Mail pieces properly accepted at the SCF before the day-zero Critical Entry Time (CET), except for mail between Puerto Rico and the U.S. Virgin Islands, and mail destined to American Samoa and the following 3-digit ZIP Code areas in Alaska (or designated portions thereof): 995 (5-digit ZIP Codes 99540 through 99599), 996, 997, 998, and 999.(c) A 2-day service standard is applied to:(1) Intra-SCF single-piece domestic First-Class Mail properly accepted before the day-zero CET if:(i) The SCF is also the origin Processing & Distribution Center or Facility (P&DC/F), or(ii) the combined drive time between the origin P&DC/F, destination Area Distribution Center (ADC), and destination SCF is 3 hours or less;(2) inter-SCF domestic First-Class Mail pieces properly accepted before the day-zero CET if the combined drive time between the origin P&DC/F, destination ADC, and destination SCF is 3 hours or less;(3) Presort First-Class Mail properly accepted before the day-zero CET with an origin and destination that are separately in Puerto Rico and the U.S. Virgin Islands; and(4) intra-SCF Presort First-Class Mail properly accepted before the day-zero CET with an origin or destination that is in American Samoa or one of the following 3-digit ZIP Code areas in Alaska (or designated portions thereof): 995 (5-digit ZIP Codes 99540 through 99599), 996, 997, 998, and 999.(d) A 3-day service standard is applied to domestic First-Class Mail pieces properly accepted before the day-zero CET, if the 1-day and 2-day service standards do not apply, the combined drive time between the origin P&DC/F, destination ADC, and destination SCF is 20 hours or less, and both the origin and the destination are within the contiguous 48 states.(e) A 4-day service standard is applied to domestic First-Class Mail pieces properly accepted before the day-zero CET, if the 1-day, 2-day, and 3-day service standards do not apply, and:(1) The combined drive time between the origin P&DC/F, destination ADC, and destination SCF is 41 hours or less, and both the origin and the destination are within the contiguous 48 states;(2) The origin is in the contiguous 48 states, and the destination is in any of the following: The city of Anchorage, Alaska (5-digit ZIP Codes 99501 through 99539); the 968 3-digit ZIP Code area in Hawaii; or the 006, 007, or 009 3-digit ZIP Code areas in Puerto Rico;(3) The origin is in the 006, 007, or 009 3-digit ZIP Code areas in Puerto Rico, and the destination is in the contiguous 48 states;(4) The origin is in Hawaii, and the destination is in Guam, or vice versa;(5) The origin is in Hawaii, and the destination is in American Samoa, or vice versa; or(6) Both the origin and destination are within Alaska.(f) A 5-day service standard is applied to all remaining domestic First-Class Mail pieces properly accepted before the day-zero CET.(g) The service standard for Outbound Single-Piece First-Class Mail InternationalTM; pieces properly accepted before the day-zero CET is equivalent to the service standard for domestic First-Class Mail pieces originating from the same 3-digit ZIP Code area and destined to the 3-digit ZIP Code area in which the designated International Service Center is located.(h) The service standard for Inbound Letter Post pieces properly accepted before the day-zero CET is equivalent to the service standard for domestic First-Class Mail pieces destined to the same 3-digit ZIP Code area and originating from the 3-digit ZIP Code area in which the designated International Service Center is located.86 FR 43952, Aug. 11, 2021, as amended at 87 FR 73469, Nov. 30, 2022 86 FR 43952, 10/1/2021; 87 FR 73469, 1/22/2023