I hope this helps. Section 1.C. pertains to DAL flying and the mainline, Section 1.D. pertains to DCI. The NWA/CAL code share and foreign code shares are not covered by this section.
Section 1.D. (IOW, DCI)
Permitted Arrangement With Domestic Carriers
1. Section 1 C. will not apply to flying performed by any domestic air carrier(s) (other than the Company) for the Company or for any affiliate on any permitted aircraft type.
Exception: If a permitted aircraft type meets the certificated passenger seat requirement of Section 1 A. 17. b. when first placed into service by a Delta Connection Carrier but is subsequently certificated for operation in the United States with a maximum passenger seating capacity in excess of 50 passenger seats, this permitted aircraft type may continue to be operated by Delta Connection Carriers as long as all Delta Connection Carriers operate such permitted aircraft type with no more than 50 passenger seats and with a maximum certificated gross takeoff weight in the United States of 65,000 or fewer pounds at all times.
2. If a domestic air carrier operates both permitted aircraft types and aircraft other than permitted aircraft types, the exemption for that domestic air carrier provided by Section 1 D. 1. will not apply unless:
a. the flying on aircraft other than permitted aircraft types is not performed for the Company within the meaning of Section 1 C., and
b. there is no reduction in the level of the Company’s then existing system scheduled aircraft block hours of flying as the result of the performance of such flying on other than a permitted aircraft type, and
c. the aircraft other than a permitted aircraft type, is either a jet aircraft configured with 70 or fewer passenger seats or a propeller driven aircraft configured with 72 or fewer passenger seats, and is operated on its own behalf or pursuant to agreement with an air carrier(s) other than the Company or an affiliate.
3. Section 1 C. will not apply to flying performed by any affiliate on permitted aircraft types.
4. At least 85% of all Delta Connection flying flight segments each month will be under 900 statute miles.
5. At least 90% of all Delta Connection flying flight segments each month will operate to or from Delta hubs, defined for this purpose as being Atlanta, Boston, Cincinnati, Washington, D.C. (DCA and IAD), Dallas-Fort Worth, Orlando, Los Angeles, Salt Lake City, New York (LGA and JFK), Fort Lauderdale, Tampa and any other airport with more than 50 daily departures of Company flying.
6. No more than 6% of Delta Connection flying flight segments each month will be between Delta hubs (as defined in Section 1 D. 5.). For purposes of Section 1 D. 6., Delta Connection flying operated between FLL and TPA, FLL and MCO, TPA and MCO will not be considered flying between Delta hubs.
7. Delta Connection flying aircraft will only bear the name "Delta" as part of a phrase referencing a Connection-type operation.